Hepatitis B Viral Variants With Reduced Susceptibility To Nucleoside Analogs And Uses Thereof

ABSTRACT

The present invention relates generally to viral variants exhibiting reduced sensitivity to particular agents and/or reduced interactivity with immunological reagents. More particularly, the present invention is directed to hepatitis B virus (HBV) variants exhibiting complete or partial resistance to nucleoside or nucleotide analogs and/or reduced interactivity with antibodies to viral surface components including reduced sensitivity to these antibodies. The present invention further contemplates assays for detecting such viral variants, which assays are useful in monitoring anti-viral therapeutic regimens and in developing new or modified vaccines directed against viral agents and in particular HBV variants. The present invention also contemplates the use of the viral variants to screen for and/or develop or design agents capable of inhibiting infection, replication and/or release of the virus.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to viral variants exhibiting reduced sensitivity to particular agents and/or reduced interactivity with immunological reagents. More particularly, the present invention is directed to hepatitis B virus (HBV) variants exhibiting complete or partial resistance to nucleoside or nucleotide analogs and/or reduced interactivity with antibodies to viral surface components including reduced sensitivity to these antibodies. The present invention further contemplates assays for detecting such viral variants, which assays are useful in monitoring anti-viral therapeutic regimens and in developing new or modified vaccines directed against viral agents and in particular HBV variants. The present invention also contemplates the use of the viral variants to screen for and/or develop or design agents capable of inhibiting infection, replication and/or release of the virus.

2. Description of the Prior Art

Bibliographic details of the publications referred to in this specification are also collected at the end of the description.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in any country.

Hepatitis B virus (HBV) can cause debilitating disease conditions and can lead to acute liver failure. HBV is a DNA virus which replicates via an RNA intermediate and utilizes reverse transcription in its replication strategy (Summers and Mason, Cell 29: 403-415, 1982). The HBV genome is of a complex nature having a partially double-stranded DNA structure with overlapping open reading frames encoding surface, core, polymerase and X genes. The complex nature of the HBV genome is represented in FIG. 1. The polymerase consists of four functional regions, the terminal protein (TP), spacer, reverse transcriptase (rt) and ribonuclease (RNAse).

The polymerase gene of HBV overlaps the envelope gene, mutations in the catalytic domain of the polymerase gene can also affect the nucleotide and the deduced amino acid sequence of the envelope protein and vice versa. In particular, the genetic sequence for the neutralization domain of HBV known as the ‘a’ determinant, which is found within the HBsAg and located between amino acids 99 and 169, actually overlaps the major catalytic regions of the viral polymerase protein and in particular domains A and B.

The presence of an HBV DNA polymerase has led to the proposition that nucleoside or nucleotide analogs could act as effective anti-viral agents. Examples of nucleoside analogs currently being tested are penciclovir and its oral form (FCV) [Vere Hodge, Antiviral Chem Chemother 4: 67-84, 1993; Boyd et al., Antiviral Chem Chemother. 32: 358-363, 1987; Kruger et al., Hepatology 22: 219A, 1994; Main et al. J Viral Hepatitis 3: 211-215, 1996], Lamivudine[(−)-β-2′-deoxy-3′-thiacytidine]; (3TC or LMV) [Severini et al., Antimicrobial Agents Chemother. 39: 430-435, 1995; Dienstag et al., New England J Med 333: 1657-1661, 1995]. New nucleoside or nucleotide analogs which have already progressed to clinical trials include the pyrimidines Emtricitabine, ((−)-β-L-2′-3′-dideoxy-5-fluoro-3′-thiacydidine; FTC), the 5-fluoro derivative of 3TC, and Clevudine (1-(2-fluoro-5-methyl-β-L-arabino-furanosyl) uracil; L-FMAU), a thymidine analog. Like 3TC, these are pyrimidine derivatives with an unnatural “L”-configuration. Several purine derivatives have also progressed to clinical trials; they include Entecavir (BMS-200, 475; ETV), a carbocyclic deoxyguanosine analog, diaminopurine dioxolane (DAPD), an oral pro-drug for dioxolane guanine ((−)-β-D-2-aminopurine dioxolane; DXG) and Adefovir dipivoxil, an oral prodrug for the acyclic deoxyadenosine monophosphate nucleoside analog Adefovir (9-[phosphonyl-methoxyethyl]-adenine; PMEA). Other drugs in pre-clinical and clinical trials include include FLG [Medivir], ACH-126,443 (L-d4C) [Archillion Pharmaceuticals], ICN 2001-3 (ICN) and Racivir (RCV) [Pharmassett].

Whilst these agents are highly effective in inhibiting HBV DNA synthesis, there is the potential for resistant mutants of HBV to emerge during long term antiviral chemotherapy. In patients on prolonged LMV therapy, key resistance mutations are selected in the rt domain within the polymerase at rtM204I/V+/−rtL180M as well as other mutations. The nomenclature used for the polymerase mutations is in accordance with that proposed by Stuyver et al., 2001, supra. LMV is a nucleoside analog that has been approved for use against chronic HBV infection. LMV is a particularly potent inhibitor of HBV replication and reduces HBV DNA titres in the sera of chronically infected patients after orthotopic liver transplantation (OLT) by inhibiting viral DNA synthesis. LMV monotherapy seems unlikely to be able to control HBV replication in the longer term. This is because emergence of LMV-resistant strains of HBV seems almost inevitable du-ring monotherapy.

Adefovir dipivoxil (ADV: formerly, bis-porn PMEA) is an orally available prodrug of the acyclic deoxyadenosine monophosphate analog adefovir (formerly, PMEA) (FIG. 2). ADV is also a potent inhibitor of HBV replication and has recently been given FDA approval for use against chronic HBV infection. Adefovir dipivoxil differs from other agents in this class in that it is a nucleotide (vs. nucleoside) analog and as such bypasses the first phosphorylation reaction during drug activation. This step is often rate-limiting. Adefovir dipivoxil has demonstrated clinical activity against both wild-type and lamivudine-resistant strains of HBV and is currently in phase III clinical Testing (Gilson et al., J Viral Hepat 6: 387-395, 1999; Perrillo et al., Hepatology 32: 129-134, 2000; Peters et al., Transplantation 68: 1912-1914, 1999; Benhamou et al., Lancet 358: 718-723, 2001). During phase II studies a 30 mg daily dose of adefovir dipivoxil resulted in a mean 4 log₁₀ decrease in viremia over 12 weeks (Heathcote et al., Hepatology 28: A620, 1998).

ADV is a substituted acyclic nucleoside phosphonate. This class of compounds also includes tenofovir disoproxil fumarate (also referred to as tenofovir DF, or tenofovir, or (TFV) or 9-R-(2-phosphonomethoxypropyl)adenine (PMPA) and is marketed as Viread by Gilead sciences).

TFV has antiviral activity against both HBV and HIV (Ying et al., J Viral Hepat. 7(2): 161-165, 2000; Ying et al., J Viral Hepat. 7(1): 79-83, 2000; Suo et al., J Biol Chem. 273(42): 27250-27258. 1998).

FTC has activity against HBV and HIV (Frick et al., Antimicrob Agents Chemother 37: 2285-229′, 1993),

Nucleoside or nucleotide analog therapy may be administered as monotherapy or combination therapy where two or more nucleoside or nucleotide analogs may be administered. The nucleoside or nucleotide analogs may also be administered in combination with other antiviral agents such as interferon or hepatitis B immunoglobulin (HBIG).

There is a need to monitor for the emergence of nucleoside/nucleotide-analog- or antibody-resistant strains of HBV and to develop diagnostic protocols to detect these resistant viruses and/or to use them to screen for and/or develop or design agents having properties making them useful as anti-viral agents. Defective forms of these resistant strains or antigenic components therefrom are also proposed to be useful in the development of therapeutic vaccine compositions as are antibodies directed to viral surface components.

SUMMARY OF THE INVENTION

Throughout this specification, unless the context requires otherwise, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

Nucleotide and amino acid sequences are referred to by a sequence identifier number (SEQ ID NO:). The SEQ ID NOs: correspond numerically to the sequence identifiers<400>1 (SEQ ID NO:1), <400>2 (SEQ ID NO:2), etc. A summary of the sequence identifiers is provided in Table 1. A sequence listing is provided after the claims.

Specific mutations in an amino acid sequence are represented herein as “Xaa₁nXaa₂” where Xaa₁ is the original amino acid residue before mutation, n is the residue number and Xaa₂ is the mutant amino acid. The abbreviation “Xaa” may be the three letter or single letter (i.e. “X”) code. An “rt” before “Xaa₁nXaa₂” means “reverse transcriptase”. An “s” means an envelope gene. The amino acid residues for HBV DNA polymerase are numbered with the residue methionine in the motif Tyr Met Asp Asp (YMDD) being residue number 204 (Stuyver et al., Hepatology 33: 751-757, 2001). The amino acid residues for hepatitis B virus surface antigen are number according to Norder et al. (J. Gen. Virol. 74: 341-1348, 1993). Both single and three letter abbreviations are used to define amino acid residues and these are summarized in Table 2.

In accordance with the present invention, the selection of HBV variants is identified in patients (Patient A, C and D) with chronic HBV infection treated with ADV and liver transplant patients (Patients B and E) treated with both ADV and LMV post-OLT or ADV post-transplant. HBV variants from Patients F, G and H were also identified following similar treatments. Variants of HBV are identified during ADV or combination ADV and LMV treatment with mutations in the HBV DNA polymerase gene which reduce the sensitivity of HBV to this nucleoside analog. Consequently, HBV rt variants are contemplated which are resistant to, or which exhibit reduced sensitivity to, ADV, LMV, TFV, FTC, ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combinations thereof. Corresponding mutations in the surface antigen also occur. The identification of these HBV variants is important for the development of assays to monitor ADV, LMV, FTC and/or TFV resistance and/or resistance to other nucleoside or nucleotide analogs or other anti-HBV agents or combinations thereof and to screen for agents which are useful as alternative therapeutic agents.

Reference herein to “anti-HBV agents” includes nucleoside and nucleotide analogs as well as immunological reagents (e.g. antibodies to HBV surface components) and chemical, proteinaceous and nucleic acid agents which inhibit or otherwise interfere with viral replication, maintenance, infection, assembly or release.

The detection of such HBV variants is particularly important in the management of therapeutic protocols including the selection of appropriate agents for treating HBV infection. The method of this aspect of the present invention is predicated in part on monitoring the development in a subject of an increased HBV load in the presence of a nucleoside or nucleotide analog or other anti-HBV agents or combinations thereof. The clinician is then able to modify an existing treatment protocol or select an appropriate treatment protocol accordingly.

Accordingly, one aspect of the present invention is directed to an isolated HBV variant comprising a nucleotide mutation in a gene encoding a DNA polymerase resulting in at least one amino acid addition, substitution and/or deletion to the DNA polymerase and which exhibits decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combinations thereof. The variant HBV comprises a mutation in an overlapping open reading frame in its genome in a region defined by one or more of domains F and G and domain A through to E of HBV DNA polymerase.

Another aspect of the present invention provides an isolated HBV variant comprising a nucleotide mutation in the S gene resulting in at least one amino acid addition, substitution and/or deletion to the surface antigen and which exhibits decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, or ADV and FTC and LMV and TFV, ADV and LMV and FTC, and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combinations thereof.

Useful mutants in the rt region include, in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131N_and rtY135C; in another embodiment, rt/N/S/T/I/V53D, rtY126Q, rtL180M, rtS202G, rtI04V and rtI235I/M; in a further embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA181T, rtK12R, rtL217R, rtS219A, rtN236T and rtN238D; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A; and in yet another embodiment, rtH90D and rtL/F108L; and in still a further embodiment, rtL157L/M, rtA181V and rtV207I and in yet a further embodiment, rtL80V, rtP109S, rtI163V, rtL229M and rtN/H/A/S/Q238K; and in another embodiment, rtS78S/T, rtN118N/S, rtN139N/K, rtV142E, rtA181A/T, rtI204M, rtQ/P/S/Stop215Q, rtE218K/E and rtN238N/H or a combination thereof or an equivalent mutation.

Other HBV variants are also contemplated with mutations in rt at rtK32, rtN33, rtP34, rtH35 and rtT37 (these are upstream of the F domain of the DNA polymerase), rtP59, rtK60, rtF61, rtA62 and rtV63 (these are located between the F and A domains), rtD83, rtV84, rtS85, rtA86, rtY89, rtH90 and rtI/L91 (these are located within the A domain and the region immediately prior to and following), rtP177, rtF178, rtL179, rtL180, rtA181, rtQ182, rtF183 and rtT184 (these are located in the B domain), rtM204 and rtY203 (these are located in the C domain), rt235, rt236, rt237, rt238 and rt239 (these are located in the D domain) and rt247, rt248, rt249, rt250 and rt251 (these are located in the E domain) or a combination thereof or an equivalent mutation.

Useful mutants are provided below (see also Tables 16 and 17):

K32M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; N33D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; P34S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; H35I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; T37W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P59S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; K60M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; F61P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; A62R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; V63A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; D83C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/deletion; V84A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; S85T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; A86R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; Y89V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; H90I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; I/L91K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/deletion; P177S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; F178P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/L/K/M/deletion; L179K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/HI/deletion; L180K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; A181R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/Y/V/deletion; Q183E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; F183P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; T184W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; Y203 V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; M204F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; L235K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N236D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; T237W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P237S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; N238D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H238I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; A238R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; S239T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; Q238E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; K239M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; L247K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N248D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H248I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; F249P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/KM/deletion; M250F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; G251H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/deletion; and V251A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/I/T/W/Y/deletion.

Reference above to “deletion” means that the first mentioned amino acid before the residue number has been deleted.

Useful mutations in the S gene include, in one embodiment, sP120T, sM125T and sT127A; in another embodiment, T118R, sM133T, sF134V sI195M, sS207R and sY225Y/C; in a further embodiment, sS126T, sM133L/M, sS143S/T, sD144A sG145A and sW172Stop; in yet a further embodiment, sN40S, sC69 Stop, sM75I, sL88P, sT118A, sW182stop, sW196L, sY206H and sY225F; and in yet another embodiment, sI81M and sP214Q; and in still another embodiment, sF83S, sL173F and sW199L; and in still yet another embodiment, sI126T, sK160R, sS174N, sA184V, sW196L, sS210N, sF/C220L and sY221C; and in yet another embodiment, sC69Stop/C, sC76Y sI110V/I, sY134N, sW172Stop/W, sW196Stop and sS207R or a combination thereof or an equivalent mutation.

The present invention further contemplates a method for determining the potential for an HBV to exhibit reduced sensitivity to ADV, LM, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof by isolating DNA or corresponding mRNA from the HBV and screening for a mutation in the nucleotide sequence encoding HBV DNA polymerase resulting in at least one amino acid substitution, deletion and/or addition in any one or more of domains F and G and domains A through to E or a region proximal thereto of the DNA polymerase and associated with resistance or decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof. The presence of such a mutation is an indication of the likelihood of resistance to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

The present invention also provides a composition comprising a variant HBV resistant to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, or ADV and FTC and LMV and TFV, ADV and LMV and FTC, and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof or an HBV surface antigen from the variant HBV or a recombinant or derivative form thereof or its chemical equivalent and one or more pharmaceutically acceptable carriers and/or diluents.

Yet another aspect of the present invention provides a use of the aforementioned composition or a variant HBV comprising a nucleotide mutation in a gene encoding a DNA polymerase resulting in at least one amino acid addition, substitution and/or deletion to the DNA polymerase and a decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof in the manufacture of a medicament for the treatment and/or prophylaxis of hepatitis B virus infection.

The present invention also contemplates a method for determining whether an HBV strain exhibits reduced sensitivity to a nucleoside or nucleotide analog or other anti-HBV agents or by isolating DNA or corresponding mRNA from the HBV and screening for a mutation in the nucleotide sequence encoding the DNA polymerase wherein the presence of the following mutations in the rt region: in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131N and rtY135C; in another embodiment, rt/N/S/T/I/V53D, rtY126Q, rtL180M, rtS202G, rtI204V and rtI235I/M; in a further embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA181T, rtK212R, rtL217R, rtS219A, rtN236T and rtN238D; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A; in still another embodiment, rtH90D and rtL/F108L, in even yet another embodiment, rtL157L/M, rtA181V and rtV2071; in still yet another embodiment, rtL80V, rtP109S, rtI163V, rtL229M and rtN/H/A/S/Q238K; in another embodiment, rtS78S/T, rtN118N/S, rtN139N/K, rtV142E, rtA181A/T, rtI204M, rtQ/P/S/Stop215Q, rtE218K/E and rtN238N/H; in a further embodiment, rtK32, rtN33, rtP34, rtH35 and rtT37; in yet another embodiment, rtP59, rtK60, rtF61, rtA62 and rtV63; in still another embodiment, rtD83, rtV84, rtS85, rtA86, rtY89, rtH90 and rtI/L91; in even yet another embodiment, rtP177, rtF178, rtL179, rtL180, rtA181, rtQ182, rtF183 and rtT184; in still yet another embodiment, rtM204 and rtY203; in another embodiment, rt235, rt236, rt237, rt238 and rt239; in a farther embodiment, rt247, rt248, rt249, rt250 and rt251 or combinations thereof or an equivalent one or more other mutation is indicative of a variant which exhibits a decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

Still a further methodology comprises screening for a mutation in the nucleotide sequence encoding the envelope genes (s) wherein the presence of the following mutations in the S gene: in one embodiment, sP120T, sM125T and sT127A; in another embodiment, sT118R, sM133T, SF134V, sI195M, sS207R and sY225Y/C; in a further embodiment, sS126T, sM133L/M, sS143SIT, sD144A, sG145A and sW172Stop in yet another embodiment, sN40S, sC69Stop, sM75I, sL88P, sT118A, sW182Stop, sW196L, sY206H and sY225F; in still yet another embodiment, s181M and sP214Q; in another embodiment, sF83S, sL173F and sW199L; in a further aspect, sI126T, sK160R, sS174N, sA184V, sW196L, sS210N, sF/C220L and sY221C; in a further embodiment, sC69Stop/C, sC76Y, sI110V/I, sY134N, sW172Stop/W, sW196Stop and sS207R or combinations thereof or an equivalent one or more other mutation is indicative of a variant which exhibits a decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV, and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

Preferably, the variants are in an isolated form such that they have undergone at least one purification step away from naturally occurring body fluid. Alternatively, the variants may be maintained in isolated body fluid or may be in DNA form. The present invention also contemplates infectious molecular clones comprising the genome or parts thereof from a variant HBV. The detection of HBV or its components in cells, cell lysates, cultured supernatant fluid and bodily fluid may be by any convenient means including any nucleic acid-based detection means, for example, by nucleic acid hybridization techniques or via one or more polymerase chain reactions (PCRs). The term “bodily fluid” includes any fluid derived from the blood, lymph, tissue or organ systems including serum, whole blood, biopsy and biopsy fluid, organ explants and organ suspension such as liver suspensions.

Another aspect of the present invention is directed to a variant HBV comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or a truncation compared to a surface antigen from a reference or wild type HBV and wherein an antibody generated to the reference or wild type surface antigen exhibits an altered immunological profile relative to the HBV variant. One altered profile includes a reduced capacity for neutralizing the HBV. More particularly, the surface antigen of the variant HBV exhibits an altered immunological profile compared to a pre-treatment HBV where the variant HBV is selected for by a nucleoside or nucleotide analog or other anti-HBV agents of the HBV DNA polymerase. The variant HBV of this aspect of the invention may also comprise a nucleotide sequence comprising a single or multiple nucleotide substitution, addition and/or deletion compared to a pre-treatment HBV.

The present invention extends to an isolated HBsAg or a recombinant form thereof or derivative or chemical equivalent thereof corresponding to the variant HBV. Generally, the HBsAg or its recombinant or derivative form or its chemical equivalent comprises an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or a truncation compared to an HBsAg from a reference HBV and wherein an antibody directed to a reference HBV exhibits an altered immunological profile to an HBV carrying said variant HBsAg. In one embodiment, the altered immunological profile comprises a reduction in the ability to neutralize the variant HBV.

Another aspect of the present invention contemplates a method for detecting an agent which exhibits inhibitory activity to an HBV by generating a genetic construct comprising a replication competent-effective amount of the genome from the HBV contained in a plasmid vector and then transfecting said cells with said construct, contacting the cells, before, during and/or after transfection, with the agent to be tested, culturing the cells for a time and under conditions sufficient for the HBV to replicate, express genetic sequences and/or assemble and/or release virus or virus-like particles if resistant to said agents; and the subjecting the cells, cell lysates or culture supernatant fluid to viral- or viral-component-detection means to determine whether or not the virus has replicated, expressed genetic material and/or assembled and/or been released in the presence of the agent. In a preferred embodiment, the plasmid vector in a baculovirus vector and the method comprises generating a genetic construct comprising a replication competent-effective amount of the genome from the HBV contained in or fused to an amount of a baculovirus genome effective to infect cells and then infecting said cells with said construct, contacting the cells, before, during and/or after infection, with the agent to be tested, culturing the cells for a time and under conditions sufficient for the HBV to replicate, express genetic sequences and/or assemble and/or release virus or virus-like particles if resistant to said agent and then subjecting the cells, cell lysates or culture supernatant fluid to viral- or viral-component-detection means to determine whether or not the virus has replicated, expressed genetic material and/or assembled and/or been released in the presence of the agent.

In connection with these methods, the plasmid vector may include genes encoding part or all of other viral vectors such as baculovirus vectors or adenovirus vectors (see Ren and Nassal, J. Virol. 75(3): 1104-1116, 2001).

In an alternative embodiment, the method comprises generating a continuous cell line comprising an infectious copy of the genome of the HBV in a replication competent effective amount such that said infectious HBV genome is stably integrated into said continuous cell line such as but not limited to the 2.2.15 or AD cell line, contacting the cells with the agent to be tested, culturing the cells for a time and under conditions sufficient for the HBV to replicate, express genetic sequences and/or assemble and/or release virus or virus-like particles if resistant to the agent and then subjecting the cells, cell lysates or culture supernatant fluid to viral- or viral-component-detection means to determine whether or not the virus has replicated, expressed genetic material and/or assembled and/or been released in the presence of the agent.

In an alternative embodiment, the present invention also contemplates a method for detecting an agent which exhibits inhibitory activity to an HBV polymerase in an in vitro polymerase assay. The HBV polymerase activity can be examined using established assays (Gaillard et al., Antimicrob Agents Chemother. 46(4): 1005-1013, 2002; Xiong et al., Hepatology. 28(6): 1669-73, 1998). The HBV polymerase may be a wild-type or reference HBV polymerase or mutant HBV polymerase.

The identification of viral variants enables the production of vaccines comprising particular recombinant viral components such as polymerases or envelope genes PreS1, PreS2, S encoding for L, M, S proteins as well as therapeutic vaccines comprising defective HBV variants. Rational drug design may also be employed to identify or generate therapeutic molecules capable of interacting with a polymerase or or envelope genes PreS1, PreS2, S encoding for L, M, S-proteins or other component of the HBV. Such drugs may also have diagnostic potential. In addition, defective HBV variants may also be used as therapeutic compositions to generate an immune response against the same, similar or homologous viruses. Alternatively, antibodies generated to the HBV variants or surface components thereof may be used in passive immunization of subjects against infection by HBV variants or similar or homologous viruses. Furthermore, agents such as nucleoside or nucleotide analogs, RNAi or siRNA molecules, antisense or sense oligonucleotides, chemical or proteinaceous molecules having an ability to down-regulate the activity of a component of HBV and inhibit replication, maintenance, infection, assembly or release are contemplated by the present invention.

A summary of the abbreviations used throughout the subject specification are provided in Table 3.

A summary of sequence identifiers used throughout the subject specification is provided in Table 1.

TABLE 1 Summary of sequence identifiers SEQUENCE ID NO: DESCRIPTION 1 Formula I 2 Formula II 3 OS1 primer 4 TTA3 primer 5 JM primer 6 TTA4 primer 7 OS2 primer 8 sense primer 9 antisense primer 10 internal regions primer 11 internal regions primer 12 PC1 forward primer 13 PC2 reverse primer 14 HBV-specific molecular beacon primer 15 ILA 1 F, A-E (FIG. 4) 16 ILA 2 F, A-E (FIG. 4) 17 ILA 3 F, A-E (FIG. 4) 18 ILA 4 F, A-E (FIG. 4) 19 Pol Trans Pre 1 (FIG. 5) 20 Pol Trans 2 (FIG. 5) 21 Pol Trans 3 (FIG. 5) 22 Pol Trans 4 (FIG. 5) 23 HBsAg Trans of Pre 1 (FIG. 6) 24 HBsAg Trans of 2 (FIG. 6) 25 HBsAg Trans of 3 (FIG. 6) 26 HBsAg Trans of 4(FIG. 6) 27 S0 (FIG. 7) 28 S6 (FIG. 7) 29 S8 (FIG. 7) 30 S12 (FIG. 7) 31 S15 (FIG. 7) 32 Pol Trans S0 (FIG. 8) 33 Pol Trans S6 (FIG. 8) 34 Pol Trans S8 (FIG. 8) 35 Pol Trans S12 (FIG. 8) 36 Pol Trans S15 (FIG. 8) 37 HBsAg Trans of S0 (FIG. 9) 38 HBsAg Trans of S6 (FIG. 9) 39 HBsAg Trans of S8 (FIG. 9) 40 HBsAg Trans of S12 (FIG. 9) 41 HBsAg Trans of S15 (FIG. 9) 42 Nucleotide sequence Patient C (FIG. 10) 43 POL Trans of Patient C (FIG. 11) 44 HBsAg Trans of Patient C (FIG. 12) 45 Nucleotide sequence of Patient D (FIG. 13) 46 Pol Trans of Patient D (FIG. 14) 47 HBsAg Trans of Patient D (FIG. 15) 48 Nucleotide sequence of Patient E (FIG. 16) 49 Pol Trans of Patient E (FIG. 17) 50 HBsAg Trans of Patient E (FIG. 18) 51 Nucleotide sequence of Patient F (FIG. 20) 52 Deduced sequence of DNA polymerase of Patient F (FIG. 21) 53 HBsAg Trans of Patient F (FIG. 22) 54 Nucleotide sequence of Patient G (FIG. 23) 55 Deduced sequence of DNA polymerase of Patient G (FIG. 24) 56 HBsAg Trans of Patient G (FIG. 25) 57 Nucleotide sequence of Patient H (FIG. 26) 58 Deduced sequence of DNA polymerase of Patient H (FIG. 27) 59 HBsAg Trans of Patient H (FIG. 28)

TABLE 2 Single and three letter amino acid abbreviations Amino Acid Three-letter Abbreviation One-letter symbol Alanine Ala A Arginine Arg R Asparagine Asn N Aspartic acid Asp D Cysteine Cys C Glutamine Gln Q Glutamic acid Glu E Glycine Gly G Histidine His H Isoleucine Ile I Leucine Leu L Lysine Lys K Methionine Met M Phenylalanine Phe F Proline Pro P Serine Ser S Threonine The T Tryptophan Trp W Tyrosine Tyr Y Valine Val V Any residue Xaa X

A list of abbreviations used throughout the subject specification are provided in Table 3.

TABLE 3 Abbreviations ABBREVIATION DESCRIPTION 3TC (LMV); (−)-β-2′-deoxy-3′-thiacytidine ADV adefovir dipivoxil DAPD diaminopurine dioxalone DXG dioxolane guanine ETV entecavir FAM famciclovir FCV famciclovir FTC emtricitabine HBIG hepatitis B immunoglobulin HBsAg hepatitis B surface antigen HBV hepatitis B virus LMV lamividuine PMEA 9-[phosphonyl-methoxyethyl]-adenine; adefovir PMPA 9-R-(2-phosphonomethoxypropyl)adenine RNase ribonuclease rt (“rt” before reverse transcriptase “Xaa₁nXaa₂” means reverse transcriptase) s (as used in a mutation, envelope gene e.g. sF134V) TFV tenofovir disoproxil fumarate YMDD Tyr Met Asp Asp-a motif in the polymerase protein; where the Met residue is designated residue number 204 of the reverse transcriptase

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagrammatic representation showing the partially double stranded DNA HBV genome showing the overlapping open reading frames encoding surface (S), core (C), polymerase (P) and X gene.

FIG. 2 is a diagrammatic representation of the chemical structure of ADV.

FIG. 3 is a diagrammatic representation of a computer system for determining the potency value (P_(A)) of a variant HBV.

FIG. 4 is a representation showing comparison of the HBV nucleotide sequence encoding the catalytic region of the polymerase gene in sequential samples from Patient A during ADV treatment.

FIG. 5 is a representation showing comparison of the deduced amino acid sequence of the catalytic region of the polymerase gene in sequential samples from Patient A during ADV therapy.

FIG. 6 is a representation showing comparison of the deduced amino acid sequence of the envelope gene in sequential samples from Patient A during ADV therapy.

FIG. 7 is a representation showing comparison of the HBV nucleotide sequence encoding the catalytic region of the polymerase gene in sequential samples from Patient B during ADV and LMV treatment.

FIG. 8 is a representation showing comparison of the deduced amino acid sequence of the catalytic region of the polymerase gene in sequential samples from Patient B during ADV and LMV therapy.

FIG. 9 is a representation showing comparison of the deduced amino acid sequence of the envelope gene in sequential samples from Patient B during ADV and LMV therapy.

FIG. 10 is a representation showing comparison of the HBV nucleotide sequence encoding the catalytic region of the polymerase gene in sequential samples from Patient C during ADV treatment.

FIG. 11 is a representation showing comparison of the deduced amino acid sequence of the catalytic region of the polymerase gene in sequential samples from Patient C during ADV therapy.

FIG. 12 is a representation showing comparison of the deduced amino acid sequence of the envelope gene in sequential samples from Patient C during ADV therapy.

FIG. 13 is a representation showing comparison of the HBV nucleotide sequence encoding the catalytic region of the polymerase gene in sequential samples from Patient D during ADV treatment.

FIG. 14 is a representation showing comparison of the deduced amino acid sequence of the catalytic region of the polymerase gene in sequential samples from Patient D during ADV therapy.

FIG. 15 is a representation showing comparison of the deduced amino acid sequence of the envelope gene in sequential samples from Patient D during ADV therapy.

FIG. 16 is a representation showing comparison of the HBV nucleotide sequence encoding the catalytic region of the polymerase gene in sequential samples from Patient E during ADV treatment.

FIG. 17 is a representation showing comparison of the deduced amino acid sequence of the catalytic region of the polymerase gene in sequential samples from Patient E during ADV therapy.

FIG. 18 is a representation showing comparison of the deduced amino acid sequence of the envelope gene in sequential samples from Patient E during ADV therapy.

FIG. 19 is a diagrammatic representation of a system used to carry out the instructions encoded by the storage medium.

FIG. 20 is a representation showing the nucleotide sequence of envelope/rt region of an HBV isolated from Patient F having ADV therapy.

FIG. 21 is a representation showing the deduced amino acid sequence of DNA polymerase encoded by the nucleotide sequence shown in FIG. 20.

FIG. 22 is a representation showing the deduced amino acid sequence of HBsAg encoded by the nucleotide sequence shown in FIG. 20.

FIG. 23 is a representation showing the nucleotide sequence of envelope/rt region of an HBV isolated from Patient G having ADV therapy.

FIG. 24 is a representation showing the deduced amino acid sequence of DNA polymerase encoded by the nucleotide sequence shown in FIG. 23.

FIG. 25 is a representation showing the deduced amino acid sequence of HBsAg encoded by the nucleotide sequence shown in FIG. 23.

FIG. 26 is a representation showing the nucleotide sequence of envelope/rt region of an HBV isolated from Patient H having ADV therapy.

FIG. 27 is a representation showing the deduced amino acid sequence of DNA polymerase encoded by the nucleotide sequence shown in FIG. 26.

FIG. 28 is a representation showing the deduced amino acid sequence of HBsAg encoded by the nucleotide sequence shown in FIG. 26.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is predicated in part on the identification and isolation of nucleoside or nucleotide analog-resistant variants of HBV following treatment of patients with either ADV or LMV or more particularly ADV and LMV, or optionally other nucleoside analogs or nucleotide analogs or other anti-HBV agents such as TFV or FTC. In particular, ADV or ADV and LMV treated patients gave rise to variants of HBV exhibiting decreased or reduced sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV. Reference herein to “decreased” or “reduced” in relation to sensitivity to ADV and/or LMV and/or FTC and/or TFV includes and encompasses a complete or substantial resistance to the nucleoside or nucleotide analog or other anti-HBV agents as well as partial resistance and includes a replication rate or replication efficiency which is more than a wild-type in the presence of a nucleoside or nucleotide analog or other anti-HBV agents. In one aspect, this is conveniently measured by an increase in viral load during treatment, or alternatively, there is no substantial decrease in HBV DNA viral load from pre-treatment HBV DNA levels during treatment (i.e., non-response to treatment).

Before describing the present invention in detail, it is to be understood that unless otherwise indicated, the subject invention is not limited to specific formulations of components, manufacturing methods, dosage regimens, or the like, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

It must be noted that, as used in the subject specification, the singular forms “a”, “an” and “the” include plural aspects unless the context clearly dictates otherwise. Thus, for example, reference to “a nucleoside or nucleotide analog” includes a single analog, as well as two or more analogs; reference to “an HBV variant” includes reference to two or more HBV variants; and so forth.

In describing and claiming the present invention, the following terminology is used in accordance with the definitions set forth below.

The terms “analog”, “compound”, “active agent”, “pharmacologically active agent”, “medicament”. “active” and “drug” are used interchangeably herein to refer to a chemical compound that induces a desired effect such as inhibit viral replication, infection, maintenance, assembly and/or the function of an enzyme such as HBV DNA polymerase. The terms also encompass pharmaceutically acceptable and pharmacologically active ingredients of those active agents specifically mentioned herein including but not limited to salts, esters, amides, prodrugs, active metabolites, analogs and the like. When the terms “analog”, “compound”, “active agent”, “pharmacologically active agent”, “medicament”, “active” and “drug” are used, then it is to be understood that this includes the active agent per se as well as pharmaceutically acceptable, pharmacologically active salts, esters, amides, prodrugs, metabolites, analogs, etc.

The present invention contemplates, therefore, compounds useful in inhibiting HBV replication, infection, maintenance, assembly and/or the function of an enzyme such as HBV DNA polymerase. Reference to an “analog”, “compound”, “active agent”, “pharmacologically active agent”, “medicament”, “active” and “drug” such as ADV, LMV, FTC and/or TFV includes combinations of two or more actives such as ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV. A “combination” also includes a two-part or more such as a multi-part anti-HBV therapeutic composition where the agents are provided separately and given or dispensed separately or admixed together prior to dispensation.

The terms “effective amount” and “therapeutically effective amount” of an agent as used herein mean a sufficient amount of the agent to provide the desired therapeutic or physiological effect of inhibiting HBV replication, infection, maintenance, assembly and/or the function of an enzyme such as HBV DNA polymerase. Furthermore, an “effective HBV-inhibiting amount” or “effective symptom-ameloriating amount” of an agent is a sufficient amount of the agent to directly or indirectly inhibit replication, infection, maintenance, assembly and/or the function of an enzyme such as HBV DNA polymerase. Undesirable effects, e.g. side effects, are sometimes manifested along with the desired therapeutic effect; hence, a practitioner balances the potential benefits against the potential risks in determining what is an appropriate “effective amount”. The exact amount required will vary from subject to subject, depending on the species, age and general condition of the subject, mode of administration and the like. Thus, it may not be possible to specify an exact “effective amount”. However, an appropriate “effective amount” in any individual case may be determined by one of ordinary skill in the art using only routine experimentation.

By “pharmaceutically acceptable” carrier, excipient or diluent is meant a pharmaceutical vehicle comprised of a material that is not biologically or otherwise undesirable, i.e. the material may be administered to a subject along with the selected active agent without causing any or a substantial adverse reaction. Carriers may include excipients and other additives such as diluents, detergents, coloring agents, wetting or emulsifying agents, pH buffering agents, preservatives, and the like.

Similarly, a “pharmacologically acceptable” salt, ester, amide, prodrug or derivative of a compound as provided herein is a salt, ester, amide, prodrug or derivative that this not biologically or otherwise undesirable.

The terms “treating” and “treatment” as used herein refer to reduction in severity and/or frequency of symptoms, elimination of symptoms and/or underlying cause, prevention of the occurrence of symptoms and/or their underlying cause, and improvement or remediation of damage in relation to HBV infection. Thus, for example, “treating” a patient involves prevention of HBV infection as well as treatment of a clinically HBV symptomatic individual by inhibiting HBV replication, infection, maintenance, assembly and/or the function of an enzyme such as HBV DNA polymerase. Thus, for example, the present method of “treating” a patient with HBV infection or with a propensity for one to develop encompasses both prevention of HBV infection as well as treating HBV infection or symptoms thereof. In any event, the present invention contemplates the treatment or prophylaxis of HBV infection.

“Patient” as used herein refers to an animal, preferably a mammal and more preferably a primate including a lower primate and even more preferably, a human who can benefit from the formulations and methods of the present invention. A patient regardless of whether a human or non-human animal may be referred to as an individual, subject, animal, host or recipient. The compounds and methods of the present invention have applications in human medicine, veterinary medicine as well as in general, domestic or wild animal husbandry. For convenience, an “animal” includes an avian species such as a poultry bird (including ducks, chicken, turkeys and geese), an aviary bird or game bird. The condition in a non-human animal may not be a naturally occurring HBV infection but HBV-like infection may be induced.

As indicated above, the preferred animals are humans, non-human primates such as marmossets, baboons, orangatangs, lower primates such as tupia, livestock animals, laboratory test animals, companion animals or captive wild animals. A human is the most preferred target. However, non-human animal models may be used.

Examples of laboratory test animals include mice, rats, rabbits, guinea pigs and hamsters. Rabbits and rodent animals, such as rats and mice, provide a convenient test system or animal model as do primates and lower primates. Livestock animals include sheep, cows, pigs, goats, horses and donkeys. Non-mammalian animals such as avian species, zebrafish, amphibians (including cane toads) and Drosophila species such as Drosophila melanogaster are also contemplated. Instead of a live animal model, a test system may also comprise a tissue culture system.

Accordingly, one aspect of the present invention is directed to an isolated HBV variant wherein said variant comprises a nucleotide mutation in a gene encoding a DNA polymerase resulting in at least one amino acid addition, substitution and/or deletion to said DNA polymerase and wherein said variant exhibits decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, or ADV and LMV and FTC, ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

HBV is a member of the Hepdnaviridae that includes also avian hepatitis viruses such as Duck hepatitis B virus (DHBV) and hepatitis viruses from mammals such as woodchuck hepatitis virus (WHV). These viruses have similarity to HBV and may be used in in vitro and in vivo or animal model systems to investigate the equivalent HBV mutants and anti-viral sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV,

An “anti-HBV agent” includes a nucleoside or nucleotide analog, protein, chemical compound, RNA or DNA or RNAi or siRNA oligonucleotide.

Preferably, the decreased sensitivity is in respect of ADV. Alternatively, the decreased sensitivity is in respect of LMV. Alternatively, the decreased sensitivity is in respect of TFV. Alternatively, the decreased sensitivity is in respect of FTC. Alternatively, the decreased sensitivity is in respect of ADV and LMV. Alternatively, the decreased sensitivity is in respect of ADV and TFV. Alternatively, the decreased sensitivity is in respect of LMV and TFV. Alternatively, the decreased sensitivity is in respect of ADV and FTC. Alternatively, the decreased sensitivity is in respect to FTC and TFV. Alternatively, the decreased sensitivity is in respect of FTC and LMV. Alternatively, the decreased sensitivity is in respect of ADV and LMV and TFV. Alternatively, the decreased sensitivity is in respect to ADV and TFV and FTC. Alternatively, the decreased sensitivity is in respect to LMV and TFV and FTC. Alternatively, the decrease sensitivity is in respect of ADV and LMV and FTC. Alternatively, the decreased sensitivity is in respect of ADV and FTC and TFV and LMV.

Reference herein to “anti-HBV agents” includes nucleoside and nucleotide analogs as well as immunological reagents (e.g. antibodies to HBV surface components) and chemical, proteinaceous and nucleic acid agents which inhibit or otherwise interfere with viral replication, maintenance, infection, assembly or release. Reference herein to “nucleic acid” includes reference to a sense or antisense molecule, RNA or DNA, oligonucleotides and RNAi and siRNA molecules and complexes containing same.

In addition to a mutation in the gene encoding DNA polymerase, due to the overlapping nature of the HBV genome (FIG. 1), a corresponding mutation may also occur in the gene encoding the S gene encoding the surface antigen (HBsAg) resulting in reduced interactivity of immunological reagents such as antibodies and immune cells to HBsAg. The reduction in the interactivity of immunological reagents to a viral surface component generally includes the absence of immunological memory to recognize or substantially recognize the viral surface component. The present invention extends, therefore, to an HBV variant exhibiting decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, and/or ADV and FTC and LMV and TFV or a reduced interactivity of an immunological reagent to HBsAg wherein the variant is selected for following ADV and/or LMV combination or sequential treatment. The term “sequential” in this respect means ADV followed by LMV and/or TFV, and/or FTC, LMV followed by ADV and/or TFV, and/or FTC, or multiple sequential administrations of each of ADV, LMV and/or TFV, and/or FTC.

A viral variant may, therefore, carry mutation only in the DNA polymerase gene or both in the DNA polymerase gene and the S gene. The term “mutation” is to be read in its broadest context and includes multiple mutations.

The present invention extends to a mutation and any domain of the HBV DNA polymerase and in particular regions F and G, and domains A through to E provided said mutation leads to decreased sensitivity to ADV and/or LMV and/or TFV or combinations thereof. Regions F and G of the HBV DNA polymerase is defined by the amino acid sequence set forth in Formula I below [SEQ ID NO:1]:

FORMULA I L, X₁, X₂, D, W, G, P, C, X₃, X₄, H, G, X₅, H, X₆, I, R, X₇, P, R, T, P, X₈, R, V, X₉, G, G, V, F, L, V, D, K, N, P, H, N, T, X₁₀, E, S, X₁₁, L, X₁₂, V, D, F, S, Q, F, S, R, G, X₁₃, X₁₄, X₁₅, V, S, W, P, K, F, A, V, P, N, L, X₁₆, 3, L, T, N, L, L, S* wherein:

X₁ is L, or R, or I X₂ is E, or D X₃ is T, or D, or A, or N, or Y X₄ is E, or D X₅ is E, or K, or Q X₆ is H, or R, or N, X₇ is I, or T X₈ is A, or S X₉ is T or R X₁₀ is A, or T, or S X₁₁ is R, or T X₁₂ is V, or G X₁₃ is S, or I, or T, or N, or V X₁₄ is T, or S, or H, or Y X₁₅ is R, or H, or K, or Q X₁₆ is Q, or P;

and wherein S* is designated as amino acid 74.

In this specification, reference is particularly made to the conserved regions of the DNA polymerase as defined by domains A to E. Regions A to E are defined by the amino acid sequence set forth in Formula II below [SEQ ED NO:2] (and in Australian Patent No. 734831):

FORMULA II S X₁ L S W L S L D V S A A F Y F H X₂ P L H P A A M P H L L X₃ G S S G L X₄ R Y V A R L S S X₅ S X₆ X₇ X N X₈ Q X₉ X₁₀ X X X X₁₁ L H X₁₂ X₁₃ C S R X₁₄ L Y V S L X₁₅ L L Y X₁₆ T X₁₇ G X₁₈ K L H L X₁₉ X₂₀ H P I X₂₁ L G F R K X₂₂ P M G X₂₃ dG L S P F L L A Q F T S A I X₂₄ X₂₅ X₂₆ X₂₇ X₂₈ R A F X₂₉ H C X₃₀ X₃₁ F X₃₂ Y M* D D X₃₃ V L G A X₃₄ X₃₅ X₃₆ X₃₇ H X₃₈ E X₃₉ L X₄₀ X₄₁ X₄₂ X₄₃ X₄₄ X₄₅ X₄₆ L L X₄₇ X₄₈ G I H L N L P X₄₉ K T K R W G Y S L N F M G Y X₅₀ I G wherein: X is any amino acid

X₁ is N or D; X₂ is I or P; X₃ is I or V; X₄ is S or D; X₅ is T or N; X₆ is R or N; X₇ is N or I; X₈ is N or Y or H; X₉ is H or Y; X₁₀ is G or R; X₁₁ is D or N; X₁₂ is D or N; X₁₃ is S or Y; X₁₄ is N or Q; X₁₅ is L or M; X₁₆ is K or Q; X₁₇ is Y or F; X₁₈ is R or W; X₁₉ is Y or L; X₂₀ is S or A; X₂₁ is I or V; X₂₂ is I or L; X₂₃ is V or G; X₂₄ is C or L; X₂₅ is A or S; X₂₆ is V or M; X₂₇ is V or T; X₂₈ is R or C; X₂₉ is F or P; X₃₀ is L or V; X₃₁ is A or V; X₃₂ is S or A; X₃₃ is V or L or M; X₃₄ is K or R; X₃₅ is S or T; X₃₆ is V or G; X₃₇ is Q or E; X₃₈ is L or S or R; X₃₉ is S or E; X₄₀ is F or Y; X₄₁ is T or A; X₄₂ is A or S; X₄₃ is V or I; X₄₄ is T or C; X₄₅ is N or S; X₄₆ is For V; X₄₇ is S or D; X₄₈ is L or V; X₄₉ is N or Q; X₅₀ is V or I; and

M* is amino acid 204; and wherein the first S is designated as amino acid 75.

Preferably, the mutation results in an altered amino acid sequence in any one or more of domains F and G, and domains A through to E or regions proximal thereto of the HBV DNA polymerase.

Another aspect of the present invention provides an BV variant comprising a mutation in an overlapping open reading frame in its genome wherein said mutation is in a region defined by one or more of domains F and G, and domains A through to E of HBV DNA polymerase and wherein said variant exhibits decreased sensitivity to ALDV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-RBV agents.

In a related embodiment, there is provided an HBV variant comprising a mutation in the nucleotide sequence encoding a DNA polymerase resulting in an amino acid addition, substitution and/or deletion in said DNA polymerase in one or more amino acids as set forth in Formula I [SEQ ID NO:1] and/or Formula II [SEQ ID NO:2]:

FORMULA I L, X₁, X₂, D, W, G, P, C, X₃, X₄, H, G, X₅, H, X₆, I, R, X₇, P, R, T, P, X₈, R, V, X₉, G, G, V, F, L, V, D, K, N, P, H, N, T, X₁₀, E, S, X₁₁, L, X₁₂, V, D, F, S, Q, F, S, R, G, X₁₃, X₁₄, X₁₅, V, S, W, P, K, F, A, V, P, N, L, X₁₆, 3, L, T, N, L, L, S* wherein:

X₁ is L, or R, or I X₂ is E, or D X₃ is T, or D, or A, or N, or Y X₄ is E, or D X₅ is E, or K, or Q X₆ is H, or R, or N, X₇ is I, or T X₈ is A, or S X₉ is T or R X₁₀ is A, or T, or S X₁₁ is R, or T X₁₂ is V, or G X₁₃ is S, or I, or T, or N, or V X₁₄ is T, or S, or H, or Y X₁₅ is R, or H, or K, or Q X₁₆ is Q, or P; and

FORMULA II S X₁ L S W L S L D V S A A F Y F H X₂ P L H P A A M P H L L X₃ G S S G L X₄ R Y V A R L S S X₅ S X₆ X₇ X N X₈ Q X₉ X₁₀ X X X X₁₁ L H X₁₂ X₁₃ C S R X₁₄ L Y V S L X₁₅ L L Y X₁₆ T X₁₇ G X₁₈ K L H L X₁₉ X₂₀ H P I X₂₁ L G F R K X₂₂ P M G X₂₃ dG L S P F L L A Q F T S A I X₂₄ X₂₅ X₂₆ X₂₇ X₂₈ R A F X₂₉ H C X₃₀ X₃₁ F X₃₂ Y M* D D X₃₃ V L G A X₃₄ X₃₅ X₃₆ X₃₇ H X₃₈ E X₃₉ L X₄₀ X₄₁ X₄₂ X₄₃ X₄₄ X₄₅ X₄₆ L L X₄₇ X₄₈ G I H L N L P X₄₉ K T K R W G Y S L N F M G Y X₅₀ I G wherein: X is any amino acid

X₁ is N or D; X₂ is I or P; X₃ is I or V; X₄ is S or D; X₅ is T or N; X₆ is R or N; X₇ is N or I; X₈ is N or Y or H; X₉ is H or Y; X₁₀ is G or R; X₁₁ is D or N; X₁₂ is D or N; X₁₃ is S or Y; X₁₄ is N or Q; X₁₅ is L or M; X₁₆ is K or Q; X₁₇ is Y or F; X₁₈ is R or W; X₁₉ is Y or L; X₂₀ is S or A; X₂₁ is I or V; X₂₂ is I or L; X₂₃ is V or G; X₂₄ is C or L; X₂₅ is A or S; X₂₆ is V or M; X₂₇ is V or T; X₂₈ is R or C; X₂₉ is F or P; X₃₀ is L or V; X₃₁ is A or V; X₃₂ is S or A; X₃₃ is V or L or M; X₃₄ is K or R; X₃₅ is S or T; X₃₆ is V or G; X₃₇ is Q or E; X₃₈ is L or S or R; X₃₉ is S or F; X₄₀ is F or Y; X₄₁ is T or A; X₄₂ is A or S; X₄₃ is V or I; X₄₄ is T or C; X₄₅ is N or S; X₄₆ is F or V; X₄₇ is S or D; X₄₈ is L or V; X₄₉ is N or Q; X₅₀ is V or I; and

M* is amino acid 204; and wherein S* in Formula I is designated as amino acid 74 and the first S in Formula II is designated as amino acid 75; and wherein said variant exhibits decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof. Preferably, the decreased sensitivity is to ADV or to both ADV and LMV or to one or both of ADV and/or LMV and/or TFV and/or FTC.

Another preferred aspect of the present invention contemplates an HBV variant comprising a mutation in the nucleotide sequence encoding HBsAg resulting in an amino acid addition, substitution and/or deletion in said HBsAg in a region corresponding to the amino acid sequence set forth in Formulae I and II wherein said variant exhibits decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

More particularly, the present invention provides a variant HBV comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or a truncation compared to a surface antigen from a reference or wild-type HBV and wherein an antibody generated to the reference or wild-type surface antigen exhibits reduced capacity for neutralizing said HBV variant, said variant selected by exposure of a subject to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

The term “combination therapy” means that both combinations of ADV, LMV, FTC and/or TFV are co-administered in the same composition or simultaneously in separate compositions. The term “sequential therapy” means that the two agents are administered within seconds, minutes, hours, days or weeks of each other and in either order. Sequential therapy also encompasses completing a therapeutic course with one or other of ADV, LMV, FTC or TFV and then completing a second or third or subsequent therapeutic courses with the other of ADV, LMV, FTC or TFV.

Accordingly, another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to ADV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to LMV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Yet another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to FTC therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Still another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to TFV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Even yet another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to ADV and LMV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Even still another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to ADV and TFV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

A further aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to LMV and TFV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to ADV and FTC therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Yet another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to TFV and FTC therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Still another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to FTC and LMV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Even yet another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to ADV, LMV and TFV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Even still another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to ADV, LMV and TFV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

A further aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to ADV, LMV and FTC therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to FTC, LMV and TFV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Yet another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to ADV, FTC and TFV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Still yet another aspect of the present invention contemplates an HBV variant comprising a surface antigen having an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or truncation compared to the pretreatment HBV and wherein the surface antigen of the variant HBV exhibits an altered immunological profile compared to the pretreatment HBV where the said variant HBV is selected for by exposure of a subject to ADV, LMV, FTC and TFV therapy or therapy by one or more other nucleoside or nucleotide analogs or other anti-HBV agents.

Preferably, the variants are in isolated form such that they have undergone at least one purification step away from naturally occurring body fluid. Alternatively, the variants may be maintained in isolated body fluid or may be in DNA form. The present invention also contemplates infectious molecular clones comprising the genome or parts thereof from a variant HBV. Furthermore, the present invention provides isolated components from the variant HBVs such as but not limited to an isolated HBsAg. Accordingly, the present invention provides an isolated HBsAg or a recombinant form thereof or derivative or chemical equivalent thereof, said HBsAg being from a variant HBV selected by exposure of a subject to one or more of ADV, LMV, FTC and/or TFV or optionally one or more nucleoside or nucleotide analogs or other anti-HBV agents.

More particularly, yet another aspect of the present invention is directed to an isolated variant HBsAg or a recombinant or derivative form thereof or a chemical equivalent thereof wherein said HBsAg or its recombinant or derivative form or its chemical equivalent exhibits an altered immunological profile compared to an HBsAg from a reference HBV, said HBsAg being from a variant HBV selected by exposure of a subject to one or more of ADV, LMV, FTC and/or TFV or optionally one or more nucleoside or nucleotide analogs or other anti-HBV agents.

Even more particularly, the present invention provides an isolated variant HBsAg or a recombinant or derivative form thereof or a chemical equivalent thereof wherein said HBsAg or its recombinant or derivative form or its chemical equivalent comprises an amino acid sequence with a single or multiple amino acid substitution, addition and/or deletion or a truncation compared to an HBsAg from a reference HBV and wherein a neutralizing antibody directed to a reference HBV exhibits no or reduced neutralising activity to an HBV carrying said variant HBsAg, said HBsAg being from a variant HBV selected by exposure of a subject to one or more of ADV, LMV, FTC and/or TFV or optionally one or more nucleoside or nucleotide analogs or other anti-HBV agents.

Preferred mutations in the HBV DNA polymerase include variants selected from patients with HBV recurrence following ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMW, ADV and LMV and FTC, or ADV and FTC and LMV and TFV treatment. Nucleoside or nucleotide analog or other anti-HBV agents treatment may occur in relation to a transplantation procedure (e.g. bone marrow transplantation (BMT) or OLT) or following treatment of patients diagnosed with hepatitis. Following selection of variants, viral loads are obtainable at levels similar to pre-treatment levels or are increasing while on therapy.

Preferred mutations include, in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131N and rtY135C; in another embodiment, rt/N/S/T/I/V53D, rtY126Q, rtL180M, rtS202G, rtI204V and rtI235I/M; in a further embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA181T, rtK212R, rtL217R, rtS219A, rtN236T and rtN238D; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A; in still another embodiment, rtH90D, and rtL/F108L; in even yet another embodiment, rtL157L/M, rtA181V and rtV207I; in still yet another embodiment, rtL80V, rtP109S, rtI163V, rtL229M and rtN/H/A/S/Q238K; in another embodiment, rtS78S/T, rtN118N/S, rtN139N/K, rtV142E, rtA181A/T, rtI204M, rtQ/P/S/Stop215Q, rtE218K/E and rtN238N/H; in a further embodiment, rtK32, rtN33, rtP34, rtH35 and rtT37; in yet another embodiment, rtP59, rtK60, rtF61, rtA62 and rtV63; in still another embodiment, rtD83, rtV84, rtS85, rtA86, rtY89, rtH90 and rtI/L91; in even yet another embodiment, rtP177, rtF178, rtL179, rtL180, rtA181, rtQ182, rtF183 and rtT184; in still yet another embodiment, rtM204 and rtY203; in another embodiment, rt235, rt236, rt237, rt238 and rt239; in a further embodiment, rt247, rt248, rt249, rt250 and rt251; in yet another embodiment,

K32M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; N33D/C/Q/E/G/H/I/L/K/M/F/S/T/W/Y/V/A/R/deletion; P34S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; H35I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; T37W/Y/V/A/R/N/D/C/Q/E/G/E/G/H/I/L/K/M/P/S/deletion; P59S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; K60M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; F61P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; A62R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/V/deletion; V63A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; D83C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/deletion; V84A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; S85T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; A86R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; Y89V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; H90I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; I/L91K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/deletion; P177S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; F178P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/L/K/M/deletion; L179K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/HI/deletion; L180K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; A181R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/Y/V/deletion; Q183E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; F183P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; T184W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/P/S/deletion; Y203V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; M204F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; L235K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N233D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; T237W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P237S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; N238D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H238I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; A238R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; S239T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/P/deletion; Q238E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; K239M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; L247K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N248D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H248I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; F249P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; M250F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; G251H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/deletion; and V251A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y.

Reference above to “deletion” means that the first mentioned amino acid before the residue number has been deleted.

Such HBV variants are proposed to exhibit a decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof. It should be noted that the nomenclature system for amino acid positions is based on the methionine residues in the YMDD motif being designated codon rtM204. This numbering system is different to that in Australian Patent No. 734831 where the methionine residue in the YMDD motif within the polymerase gene is designated codon 550. In this regard, rtL180M and rtM204V correspond to L526M and M550V, respectively, in Australian Patent No. 734831. Corresponding mutations may also occur in envelope genes such as in one or more of PreS1, PreS2 and S. The mutations in S gene encoding HBsAg at sT118R, sP120T, sS143S/T, sD144A or sI195M also result in mutation in the in the polymerase gene rtY126C, rtT128N, rtF151S/F or rtM204V respectively.

Another potential mode of action of ADV and other acyclic nucleoside phosphonates is that of immune stimulation (Calio et al., Antiviral Res. 23: 77-89, 1994). A number of mutations resulted in changes in the envelope gene detected in HBV variants which may be associated with immune escape. These changes include sT118R, sP120T, sS126T, sM133T, sM133L/M, sF134V, sS143S/T, sD144A, sG145A and/or sW172STOP.

HBV encoding the mutation at codon sG145R is a well characterized vaccine escape mutant, although the envelope protein from HBV encoding the mutation at sG145A does not have the same antigen/antibody binding characteristics as the sG145R. This mutation was detected in HBV isolated from patient C in conjunction with mutations at codons 143 and 144.

The identification of the variants of the present invention permits the generation of a range of assays to detect such variants. The detection of such variants may be important in identifying resistant variants to determine the appropriate form of chemotherapy and/or to monitor vaccination protocols, or develop new or modified vaccine preparations.

Still another aspect of the present invention contemplates a method for determining the potential for an HBV to exhibit reduced sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents, said method comprising isolating DNA or corresponding mRNA from said HBV and screening for a mutation in the nucleotide sequence encoding HBV DNA polymerase resulting in at least one amino acid substitution, deletion and/or addition in any one or more of domains F and G, and A domains through to E or a region proximal thereto of said DNA polymerase and associated with resistance or decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents wherein the presence of such a mutation is an indication of the likelihood of resistance to said ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents.

Preferably, the assay detects one or more of the following mutations: in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131M and rtY135C; in another embodiment, rI/N/S/T/I/V53D, rtY126Q, rtL180M, rtS202G, rtI204V and rtI235I/M; in a further embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA181T, rtK212R, rtL217R, rtS219A, rtN236T and rtN238D; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A; in still another embodiment, rtH90D and rtL/F108L; in even yet another embodiment, sP120T, sM125T and sT127A; in still yet another embodiment, sT118R, sM133T, SF134V, sI195M, sS207R and sY225Y/C; in another embodiment, sS126T, sM133L/M, sS143S/T, sD144A, sGI45A and sW172Stop; in a further embodiment, sN40S, sC69STOP, sM751, sL88P, sT118A, sW182Stop, sW196L, sY206H and sY225F; in yet another embodiment, s181M and sP214Q; in still another embodiment, sF83S, sL173F and sW199L; in yet another embodiment, sI126T, sK160R, sS174N, sA184V, sW196L, sS210N, sF/C220L and sY221C; in still another embodiment, sC69Stop/C, sC76Y, sI110V/I, sY134N, sW172Stop/W, sW196Stop, sS207R; in even still another embodiment, rtK32, rtN33, rtP34, rtH35 and rtT37); in another embodiment, rtP59, rtK60, rtF61, rtA62 and rtV63); in a further embodiment, rtD83, rtV84, rtS85, rtA86, rtY89, rtH90 and rtI/L91); in yet another embodiment, rtP177, rtF178, rtL179, rtL180, rtA181, rtQ182, rtF183 and rtT184; in still another embodiment, rtM204 and rtY203; in even yet another embodiment, rt235, rt236, rt237, rt238 and rt239 and in even still another embodiment, rt247, rt24S, rt249, rt250 and rt251 and in another embodiment,

K32M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; N33D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; P34S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletionF; H35I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; T37W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P59S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; K60M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; F61P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; A62R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; V63A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; D83C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/deletion; V84A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; S85T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; A86R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; Y89V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; H90I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; I/L91K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/deletion; P177S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; F178P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; L179K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; L180K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; A181R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; Q183E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; F183P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; T184W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; Y203V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; M204F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; L235K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N236D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; T237W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P237S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/L/L/K/M/F/deletion; N238D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H238I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; A238R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; S239T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/P/deletion; Q238E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; K239M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; L247K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N248D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H248I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; F249P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; M250F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; G251H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/deletion; and

V251A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion or combinations thereof or an equivalent one or more other mutation is indicative of a variant wherein said variant exhibits a decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

Accordingly, another aspect of the present invention produces a method for determining whether an HBV strain exhibits reduced sensitivity to a nucleoside or nucleotide analog or other anti-HBV agents, said method comprising isolating DNA or corresponding mRNA from said HBV and screening for a mutation in the nucleotide sequence encoding the DNA polymerase and/or a corresponding region of the S gene, wherein the presence of a mutation selected from, in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131N and rtY135C; in another embodiment, rt/N/S/T/I/V53D, rtA126Q, rtL180M, rtS202G, rtI204V and rtI235I/M; in a further embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA181T, rtK212R, rtL217R, rtS219A, rtN236T and rtN23SD; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A; in still another embodiment, rtH90D and rtL/F108L; in even yet another embodiment, sP120T, sM125T and sT127A; in still yet another embodiment, sT118R, sM133T, SF134V, sI195M, sS207R and sY225Y/C; in another embodiment, sS126T, sM133L/M, sS143S/T, sD144A, sG145A and sW172Stop; in a further embodiment, sN40S, sC69STOP, sM75I, sL88P, sT118A, sW182Stop, sW196L, sY206H and sY225F; in yet another embodiment, s181M and sP214Q; in still another embodiment, sF83S, sL173F and sW199L; in yet another embodiment, sI126T, sK160R, sS174N, sA184V, sW196L, sS210N, sF/C220L and sY221C; in still another embodiment, sC69Stop/C, sC76Y, sI110V/I, sY134N, sW172Stop/W, sW196Stop, sS207R; in even still another embodiment, rtK32, rtN33, rtP34, rtH35 and rtT37); in another embodiment, rtP59, rtK60, rtF61, rtA62 and rtV63); in a further embodiment, rtD83, rtV84, rtS85, rtA86, rtY89, rtH90 and rtV/L91); in yet another embodiment, rtP177, rtF178, rtL179, rtL180, rtA181, rtQ182, rtF183 and rtT184; in still another embodiment, rtM204 and rtY203; in even yet another embodiment, rt235, rt236, rt237, rt238 and rt239 and in even still another embodiment, rt247, rt248, rt249, rt250 and rt251; and in another embodiment,

K32M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; N33D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; P34S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; H35I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; T37W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P59S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; K60M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; F61P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; A62R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; V63A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; D83C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/deletion; V84A R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; 85T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; A86R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; Y89V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; H90I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; I/L91K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/deletion; P177S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; F178P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/L/K/M/deletion; L179K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/HI/deletion; L180K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; A181R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; Q183E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; F183P/S/T/W/Y/V/A/R/N/D/C/Q/E/Q/G/H/I/L/K/M/deletion; T184W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/P/S/deletion; Y203V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; M204F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; L235K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N233D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; T237W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P237S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; N238D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H238I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; A238R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; S239T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/P/deletion; Q238E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; K239M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; L247K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N248D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H248I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; F249P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; M250F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; G251H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/deletion; and

V251A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion or combinations thereof or an equivalent one or more other mutation is indicative of a variant which exhibits a decreased sensitivity to ADV, LMV, TFV, or FTC or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

A farther aspect of the present invention produces a method for determining whether an HBV strain exhibits reduced sensitivity to a nucleoside or nucleotide analog or other anti-HBV agents, said method comprising isolating DNA or corresponding mRNA from said HBV and screening for a mutation in the nucleotide sequence encoding the DNA polymerase and/or a corresponding region of the S gene, wherein the presence of a mutation selected from, in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131N and rtY135C; in another embodiment, rt/N/S/T/I/V53D, rtY126Q, rtL180M, rtS202G, rtI204V and rtI235I/M; in a further embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA181T, rtK212R, rtL217R, rtS219A, rtN236T and rtN238D; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A; in still another embodiment, rtH90D and rtL/F108L; in even yet another embodiment, sP120T, sM125T and sT127A; in still yet another embodiment, sT118R, sM133T, SF134V, sI195M, sS207R and sY225Y/C; in another embodiment, sS126T, sM133L/M, sS143S/T, sD144A, sG145A and sW172Stop; in a further embodiment, sN40S, sC69STOP, sM751, sL88P, sT118A, sW182Stop, sW196L, sY206H and sY295F; in yet another embodiment, s181M and sP214Q; in still another embodiment, sF83S, sL173F and sW199L; in yet another embodiment, sI126T, sK160R, sS174N, sA184V, sW196L, sS210N, sF/C220L and sY221C; in still another embodiment, sC69Stop/C, sC76Y, sI110V/I, sY134N, sW172Stop/W, sW196Stop, sS207R; in even still another embodiment, rtK32, rtN33, rtP34, rtH35 and rtT37); in another embodiment, rtP59, rtK60, rtF61, rtA62 and rtV63); in a further embodiment, rtDS3, rtV84, rtS85, rtA86, rtY89, rtH90 and rI/L91); in yet another embodiment, rtP177, rtF178, rtL179, rtL180, rtA181 rtQ182, rtF183 and rtT184; in still another embodiment, rtM204 and rtY203; in even yet another embodiment, rt235, rt236, rt237, rt238 and rt239 and in even still another embodiment, rt247, rt248, rt249, rt250 and rt251; and in another embodiment,

K32M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; N33 D/C/Q/E/G/H/I/L/K/M/P/S/T/W/Y/V/A/R/deletion; P34S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; H35I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; T37W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P59S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; K60M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; F61P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; A62R/N/D/C/Q/E/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; V63A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; D83C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/deletion; V84A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; S85T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; A86R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; Y89V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; H90I/L/K/M/F/P/S/T/W/Y/A/R/N/D/C/Q/E/G/H/deletion; I/L91K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/deletion; P177S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; F178P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; L179K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; L180K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/HI/deletion; A181R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; Q183E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; F183P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; T184W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; Y203V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; M204F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; L235K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N236D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; T237W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P237S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; N238D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H238I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; A238R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; S239T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; Q238E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; K239M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; L247K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N248D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H248I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; F249P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/KM/deletion; M250F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; G251H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/deletion; and

V251A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/I/T/W/Y/deletion or combinations thereof or an equivalent one or more other mutation is indicative of a variant which exhibits a decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

The detection of HBV or its components in cells, cell lysates, cultured supernatant fluid and bodily fluid may be by any convenient means including any nucleic acid-based detection means, for example, by nucleic acid hybridization techniques or via one or more polymerase chain reactions (PCRs). The term “bodily fluid” includes any fluid derived from the blood, lymph, tissue or organ systems including serum, whole blood, biopsy and biopsy fluid, organ explants and organ suspension such as liver suspensions. The invention further encompasses the use of different assay formats of said nucleic acid-based detection means, including restriction fragment length polymorphism (RFLP), amplified fragment length polymorphism (AFLP), single-strand chain polymorphism (SSCP), amplification and mismatch detection (AMD), interspersed repetitive sequence polymerase chain reaction (IRS-PCR), inverse polymerase chain reaction (iPCR) and reverse transcription polymerase chain reaction (RT-PCR), amongst others. Other forms of detection include Northern blots, Southern blots, PCR sequencing, antibody procedures such as ELISA, Western blot and immunohistochemistry. A particularly useful assay includes the reagents and components required for immobilized oligonucleotide- or oligopeptide-mediated detection systems.

One particularly useful nucleic acid detection system is the reverse hybridization technique. In this technique, DNA from an HBV sample is amplified using a biotin or other ligand-labeled primer to generate a labeled amplification. Oligonucleotides immobilized to a solid support such as a nitrocellulose film are then used to capture amplified DNA by hybridization. Specific nucleic acid fragments are identified via biotin or the ligand. Generally, the labeled primer is specific for a particular nucleotide variation to be detected. Amplification occurs only if the variation to be detected is present. There are many forms of the reverse hybridization assay and all are encompassed by the present invention.

Detecting HBV replication in cell culture is particularly useful.

This and other aspects of the present invention is particularly amenable to microarray analysis such as to identify oligonucleotides including sense and antisense molecules, RNAi or siRNA molecules or DNA or RNA-binding molecules which down-regulate genomic sequences or transcripts of HBV. Microarray analysis may also be used to identify particular mutations in the HBV genome such as within the HBV DNA polymerase-coding region or the HBsAg-coding region.

Another aspect of the present invention contemplates a method for detecting an agent which exhibits inhibitory activity to an HBV by:

-   -   generating a genetic construct comprising a replication         competent-effective amount of the genome from the HBV contained         in a plasmid vector and then transfecting said cells with said         construct;     -   contacting the cells, before, during and/or after transfection,         with the agent to be tested;     -   culturing the cells for a time and under conditions sufficient         for the HBV to replicate, express genetic sequences and/or         assemble and/or release virus or virus-like particles if         resistant to said agents; and     -   then subjecting the cells, cell lysates or culture supernatant         fluid to viral- or viral-component-detection means to determine         whether or not the virus has replicated, expressed genetic         material and/or assembled and/or been released in the presence         of the agent.

In a preferred embodiment, the plasmid vector may include genes encoding part or all of other viral vectors such as baculovirus or adenovirus (Ren and Nassal, 2001, supra) and the method comprises:

-   -   generating a genetic construct comprising a replication         competent-effective amount of the genome from the HBV contained         in or fused to an amount of a baculovirus genome or adenovirus         genome effective to infect cells and then infecting said cells         with said construct;     -   contacting the cells, before, during and/or after infection,         with the agent to be tested;     -   culturing the cells for a time and under conditions sufficient         for the HBV to replicate, express genetic sequences and/or         assemble and/or release virus or virus-like particles if         resistant to said agent; and     -   then subjecting the cells, cell lysates or culture supernatant         fluid to viral- or viral-component-detection means to determine         whether or not the virus has replicated, expressed genetic         material and/or assembled and/or been released in the presence         of the agent.

In an alternative embodiment, the method comprises:

-   -   generating a continuous cell line comprising an infectious copy         of the genome of the HBV in a replication competent effective         amount such that said infectious HBV genome is stably integrated         into said continuous cell line such as but not limited to 2.2.15         or AD;     -   contacting the cells with the agent to be tested;     -   culturing the cells for a time and under conditions sufficient         for the HBV to replicate, express genetic sequences and/or         assemble and/or release virus or virus-like particles if         resistant to the agent; and     -   then subjecting the cells, cell lysates or culture supernatant         fluid to viral- or viral-component-detection means to determine         whether or not the virus has replicated, expressed genetic         material and/or assembled and/or been released in the presence         of the agent.

The above-mentioned methods are particularly useful in identifying or developing agents against HBV variants such as those carrying mutations, in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131N and rtY135C; in another embodiment, rt/N/S/T/I/V53D, rtY126Q, rtL180M, rtS202G, rtI204V and rtI235I/M; in a further embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA181T, rtK212R, rtL217R, rtS219A, rtN236T and rtN238D; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A; in still another embodiment rtH90D and rtL/F108L; in even yet another embodiment, rtL157L/M, rtA181V and rtV207I; in even still another embodiment, rtL80V, rtP109S, rtI163V, rtL229M and rtN/H/A/S/Q238K; in another embodiment, rtS78S/T, rtN118N/S, rtN139N/K, rtV142E, rtA181A/T, rtI204M, rtQ/P/S/Stop215Q, rtE218K/E and rtN238N/H; in a further embodiment, sP120T, sM125T and sT127A; in yet another embodiment, sT118R, sM133T, SF134V, sI195M, sS207R and sY225Y/C; in still another embodiment, sS126T, sM133L/M, sS143S/T, sD144A, sG145A and sW172Stop; in even yet another embodiment, sN40S, sC69Stop, sM75L, sL88P, sT118A, sW182STOP, sW196L, sY206H and sY225F; in even still another embodiment, s181M and sP214Q; in another embodiment, sF83S, sL173F and sW199L; in a further embodiment, sI126T, sK160R, sS174N, sA184V, sW196L, sS210N, sF/C220L and sY221C; in yet another embodiment, sC69Stop/C, sC76Y sI110V/I, sY134N, sW172Stop/W, sW196Stop and sS207R; in still another embodiment, rtK32, rtN33, rtP34, rtH35 and rtT37; in even yet another embodiment, rtP59, rtK60, rtF61, rtA62 and rtV63; in even still another embodiment, rtD83, rtV84, rtS85, rtA86, rtY89, rtH90 and rtI/L91; in another embodiment, rtP177, rtF178, rtL179, rtL180, rtA181, rtQ182, rtF183 and rtT184; in a further embodiment, rtM204 and rtY203; in yet another embodiment, rt235, rt236, rt237, rt238 and rt239 in still another embodiment, rt247, rt248, rt249, rt250 and rt251; and in even yet another embodiment, K32M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/IL/deletion;

N33D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; P34S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; H35I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; T37W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P59S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; K60M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; F61P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; A62R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; V63A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; D83C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/deletion; V84A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; S85T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; A86R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; Y89V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; H90I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; I/L91K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/deletion; P177S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; F178P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/L/K/M/deletion; L179K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/HI/deletion; L180K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; A181R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/Y/V/deletion; Q183E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; F183P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; T184W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; Y203 V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; M204F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; L235K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N236D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; T237W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P237S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; N238D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H238I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; A238R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; S239T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; Q238E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; K239M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; L247K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N248D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H248I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; F249P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; M250F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; G251H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/deletion; and V251A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion.

Accordingly, another aspect of the present invention contemplates a method for determining whether an HBV strain exhibits reduced sensitivity to a nucleoside or nucleotide analog or other potential anti-HBV agent, said method comprising isolating DNA or corresponding mRNA from said HBV and screening for a mutation in the nucleotide sequence of the envelope genes or DNA polymerase gene selected from, in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131N and rtY135C; in another embodiment, rt/N/S/T/I/V53D, rtY126Q, rtL180M, rtS202G, rtI204V and rtI235I/M; in a further embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA158T, rtK212R, rtL217R, rtS219A, rtN236T and rtN238D; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A; in still another embodiment rtH90D and rtL/F108L; in even yet another embodiment, rtL157L/M, rtA181V and rtV207I; in even still another embodiment, rtL80V, rtP109S, rtI163V, rtL229M and rtN/H/A/S/Q238K; in another embodiment, rtS78S/T, rtN118N/S, rtN139N/K, rtV142E, rtA181A/T, rtI204M, rtQ/P/S/Stop215Q, rtE218K/E and rtN238N/H; in a further embodiment, sP120T, sM125T and sT127A; in yet another embodiment, sT118R, sM133T, SF134V, sI195M, sS207R and sY225Y/C; in still another embodiment, sS126T, sM133L/M, sS143S/T, sD144A, sG145A and sW172Stop; in even yet another embodiment, sN40S, sC69Stop, sM75I, sL88P, sT118A, sW182STOP, sW196L, sY206H and sY225F; in even still another embodiment, s181M and sP214Q; in another embodiment, sF83S, sL173F and sWI199L; in a further embodiment, sI126T, sK160R, sS174N, sA184V, sW196L, sS200N, sF/C220L and sY221C; in yet another embodiment, sC69Stop/C, sC76Y sI110V/I, sY134N, sW172Stop/W, sW196Stop and sS207R; in still another embodiment, rtK32, rtN33, rtP34, rtH35 and rtT37; in even yet another embodiment, rtP59, rtK60, rtF61, rtA62 and rtV63; in even still another embodiment, rtD83, rtV84, rtS85, rtA86, rtY89, rtH90 and rtI/L91; in another embodiment, rtP177, rtF178, rtL179, rtL180, rtA181, rtQ182, rtF183 and rtT184; in a further embodiment, rtM204 and rtY903; in yet another embodiment, rt235, rt236, rt237, rt238 and rt239 in still another embodiment, rt247, rt248, rt249, rt250 and rt251; and in even yet another embodiment,

K32M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; N33D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; P34S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; H35I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; T37W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P59S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; K60M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; F61P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; A62R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; V63A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; D83C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/deletion; V84A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; S85T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; A86R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; Y89V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; H90I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; I/L91K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/deletion; P177S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; F178P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/L/K/M/deletion; L179K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/HI/deletion; L180K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; A181R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/Y/V/deletion; Q183E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; F183P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; T184W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; Y203 V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; M204F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; L235K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N236D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; T237W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P237S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; N238 D/C/Q/E/G/H/I/L K/M/F/P/S/T/W/Y/V/A/R/deletion; H238I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; A238R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; S239T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; Q238E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; K239M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; L247K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N248D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H248I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; F249P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/KM/deletion; M250F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; G251H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/deletion; and

V251A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/I/T/W/Y/deletion or combinations thereof or an equivalent one or more other mutation is indicative of a variant wherein said variant exhibits a decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof.

The detection of amino acid variants of DNA polymerase is conveniently accomplished by reference to the amino acid sequence shown in Formulae I and II. The polymorphisms shown represent the variations shown in various databases for active pathogenic HBV strains. Where an HBV variant comprises an amino acid different to what is represented, then such an isolate is considered a putative HBV variant having an altered DNA polymerase activity.

The present invention further contemplates agents which inhibit ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV resistant HBV variants. Such agents are particularly useful if long term treatment by ADV, LMV, FTC and/or TFV and/or optionally other nucleoside analogs or nucleotide analogs such as TFV is contemplated by the clinician. The agents may be DNA or PNA or proteinaceous or non-proteinaceous chemical molecules. Natural product screening such as from plants, coral and microorganisms is also contemplated as a useful potential source of masking agents as is the screening of combinatorial or chemical libraries. The agents may be in isolated form or in the form of a pharmaceutical composition or formulation and may be administered in place of or sequentially or simultaneously with a nucleoside or nucleotide analog. Furthermore, rationale drug design is contemplated including solving the crystal or NMR structure of, for example, HBV DNA polymerase and designing agents which can bind to the enzyme's active site. This approach may also be adapted to other HBV components.

Accordingly, another aspect of the present invention contemplates a method for detecting an agent which exhibits inhibitory activity to an HBV which exhibits resistance or decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LTV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof, said method comprising:

-   -   generating a genetic construct comprising a replication         competent-effective amount of the genome from said HBV contained         in a plasmid vector and then transfecting said cells with said         construct;     -   contacting said cells, before, during and/or after transfection,         with the agent to be tested;     -   culturing said cells for a time and under conditions sufficient         for the HBV to replicate, express genetic sequences and/or         assemble and/or release virus or virus-like particles if         resistant to said agent; and     -   subjecting the cells, cell lysates or culture supernatant fluid         to viral- or viral-component-detection means to determine         whether or not the virus has replicated, expressed genetic         material and/or assembled and/or been released in the presence         of said agent.

Still another aspect of the present invention provides a method for detecting an agent which exhibits inhibitory activity to an HBV which exhibits resistance or decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof, said method comprising:

-   -   generating a genetic construct comprising a replication         competent-effective amount of the genome from said E-BV         contained in or fused to an amount of a baculovirus genome         effective to infect cells and then infecting said cells with         said construct;     -   contacting said cells, before, during and/or after infection,         with, the agent to be tested;     -   culturing said cells for a time and under conditions sufficient         for the HBV to replicate, express genetic sequences and/or         assemble and/or release virus or virus-like particles if         resistant to said agent; and     -   subjecting the cells, cell lysates or culture supernatant fluid         to viral- or viral-component-detection means to determine         whether or not the virus has replicated, expressed genetic         material and/or assembled and/or been released in the presence         of said agent.

Preferably, the HBV genome is stably integrated into the cells' genome.

Particularly useful cells are 2.2.15 cells (Price et al., Poc. Natl. Acad. Sci. USA 86(21): 8541-8544, 1989 or AD cells (also known as HepAD32 cells or HepAD79 cells [Ying et al., Viral Hepat. 7(2): 161-165, 2000.

Whilst the baculovirus vector is a particularly useful in the practice of the present invention, the subject invention extends to a range of other vectors such as but not limited to adenoviral vectors.

The present invention further extends to cell lines (e.g. 2.2.15 or AD cells) carrying genetic constructs comprising all or a portion of an HBV genome or a gene or part of a gene therefrom.

The present invention also provides for the use of the subject HBV variants to screen for anti-viral agents. These anti-viral agents inhibit the virus. The term “inhibit” includes antagonizing or otherwise preventing infection, replication, assembly and/or release or any intermediate step. Preferred anti-viral agents include nucleoside or nucleotide analogs or anti-HBV agents, however, the present invention extends to non-nucleoside molecules.

In addition, rational drug design is also contemplated to identify or generate chemical molecules which either mimic a nucleoside or which interact with a particular nucleotide sequence or a particular nucleotide. Combinatorial chemistry and two hybrid screening are some of a number of techniques which can be employed to identify potential therapeutic or diagnostic agents.

In one example, the crystal structure or the NMR structure of polymerase or the surface antigen is used to rationally design small chemical molecules likely to interact with key regions of the molecule required for function and/or antigenicity. Such agents may be useful as inhibitors of polymerase activity and/or may alter an epitope on the surface antigen.

Several models of the HBV polymerase have been prepared due to the similarity with reverse transcriptase from HIV (Das et al., J. Virol. 75(10). 4771-4779, 2001; Barthtolomeusz et al., Intervirology 40(5-6): 337-342 1997; Allen et al., Hepatology 27(6): 1670-1677, 1998). The models of the HBV polymerase can be used for the rational drug design of flew agents effective against HBV encoding the resistant mutations as well as wild type virus. The rational drug that is designed may be based on a modification of an existing antiviral agent such as the agent used in the selection of the HBV encoding the mutations associated with resistance. Viruses or clones expressing HBV genomic material encoding the mutations may also be used to screen for new antiviral agents.

In an alternative embodiment, the present invention also contemplates a method for detecting an agent which exhibits inhibitory activity to an HBV polymerase in an in vitro polymerase assay. The HBV polymerase activity can be examined using established assays (Gaillard et al., Antimicrob Agents Chemother. 46(4). 1005-1013, 2002; Xiong et al., Hepatology; 28(6): 1669-1673, 1998).

As indicated above, microarray technology is also a useful means of identifying agents which are capable of interacting with defined HBV internal or external components. For example, arrays of HBV DNA polymerase or peptide fragments thereof carrying different amino acid variants may be used to screen for agents which are capable of binding or otherwise interacting with these molecules. This is a convenient way of determining the differential binding patterns of agents between HBV variants. Arrays of antibodies may also be used to screen for altered HBsAg molecules. Microarrays are also useful in proteomic analysis to identify molecules such as antibodies, interferons or cytokines which have an ability to interact with an HBV component. Microarrays of DNA and RNA molecules may also be employed to identify sense and antisense molecules for genetic regions on the HBV genome or transcripts thereof.

The above methods are particularly useful in identifying an inhibitor of an HBV resistant to or exhibiting reduced sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof. The present invention extends, therefore, to compositions of the inhibitors. The inhibitors may also be in the form of antibodies or genetic molecules such as ribozymes, antisense molecules and/or sense molecules for co-suppression or the induction of RNAi or may be other nucleoside or nucleotide analogs or other anti-HBV agents or derivatives of known analogs. Reference to RNAi includes reference to short, interfering RNAs (siRNA).

The term “composition” includes a “pharmaceutical composition” or a formulation.

The inhibitor is referred to below as an “active ingredient” or “active compound” and may be selected from the list of inhibitors given above.

The composition may include an antigenic component of the HBV, a defective HBV variant or an agent identified through natural product screening or rational drug design (including combinatorial chemistry).

Pharmaceutically acceptable carriers and/or diluents include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents and the like. The use of such media and agents for pharmaceutical active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active ingredient, use thereof in the therapeutic compositions is contemplated. Supplementary active ingredients can also be incorporated into the compositions.

The pharmaceutical composition may also comprise genetic molecules such as a vector capable of transfecting target cells where the vector carries a nucleic acid molecule capable of encoding an aspartyl protease inhibitor. The vector may, for example, be a viral vector.

Pharmaceutical forms suitable for injectable use include sterile aqueous solutions (where water soluble) and sterile powders for the extemporaneous preparation of sterile injectable solutions. It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteria and fungi. The carrier can be a solvent or dilution medium comprising, for example, water, ethanol, polyol (for example, glycerol, propylene glycol and liquid polyethylene glycol, and the like), suitable mixtures thereof and vegetable oils. The proper fluidity can be maintained, for example, by the use of superfactants. The preventions of the action of microorganisms can be brought about by various anti-bacterial and anti-fungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thirmerosal and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminium monostearate and gelatin.

Sterile injectable solutions are prepared by incorporating the active compounds in the required amount in the appropriate solvent with the active ingredient and optionally other active ingredients as required, followed by filtered sterilization or other appropriate means of sterilization. In the case of sterile powders for the preparation of sterile injectable solutions, suitable methods of preparation include vacuum drying and the freeze-drying technique which yield a powder of active ingredient plus any additionally desired ingredient.

When the active ingredient is suitably protected, it may be orally administered, for example, with an inert diluent or with an assimilable edible carrier, or it may be enclosed in hard or soft shell gelatin capsule, or it may be compressed into tablets. For oral therapeutic administration, the active ingredient may be incorporated with excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers and the like. Such compositions and preparations should contain at least 1% by weight of active compound. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 5 to about 80% of the weight of the unit. The amount of active compound in such therapeutically useful compositions is such that a suitable dosage will be obtained. Preferred compositions or preparations according to the present invention are prepared so that an oral dosage unit form contains between about 0.1 μg and 200 mg of active compound. Alternative dosage amounts include from about 1 μg to about 1000 mg and from about 10 μg to about 500 mg. These dosages may be per individual or per kg body weight. Administration may be per hour, day, week, month or year.

The tablets, troches, pills, capsules and the like may also contain the components as listed hereafter. A binder such as gum, acacia, corn starch or gelatin; excipients such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid and the like; a lubricant such as magnesium stearate; and a sweetening agent such as sucrose, lactose or saccharin may be added or a flavouring agent such as peppermint, oil of wintergreen or cherry flavouring. When the dosage unit form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier. Various other materials may be present as coatings or to otherwise modify the physical form of the dosage unit. For instance, tablets, pills or capsules may be coated with shellac, sugar or both. A syrup or elixir may contain the active compound, sucrose as a sweetening agent, methyl and propylparabens as preservatives, a dye and a flavouring. Of course, any material used in preparing any dosage unit form should be pharmaceutically pure and substantially non-toxic in the amounts employed. In addition, the active compound(s) may be incorporated into sustained-release preparations and formulations.

As stated above, the present invention further extends to an isolated HBsAg from the HBV variants herein described. More particularly, the present invention provides an HBsAg or a recombinant form thereof or derivative or chemical equivalent thereof. The isolated surface component and, more particularly, isolated surface antigen or its recombinant, derivative or chemical equivalents are useful in the development of biological compositions such as vaccine formulations.

Yet another aspect of the present invention provides a composition comprising a variant HBV resistant to ADV, LMVI, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or an HBV surface antigen from said variant HBV or a recombinant or derivative form thereof or its chemical equivalent and one or more pharmaceutically acceptable carriers and/or diluents. Such a composition may be regarded as a therapeutic composition and is useful in generating an immune response including a humoral response. Generally, the HBV variants are “defective” and in themselves are unable to cause a sustained infection in a subject.

As indicated above, antibodies may be generated to the mutant HBV agents and used for passive or direct vaccination against infection by these viruses. The antibodies may be generated in humans or nonhuman animals. In the case of the latter, the non-human antibodies may need to be deimmunized or more specifically humanized prior to use. Deimmunized may include, for example, grafting complimentarity determining regions (CDRs) from the variable region of a murine or non-human animal anti-HBV antibody onto a human consensus fragment antibody binding (Fab) polypeptide. Alternatively, amino acids defining epitopes in the variable region of the antibody may be mutated so that the epitopes are no longer recognized by the human MHC II complex.

Insofar as ribozyme, antisense or co-suppression (RNAi) or siRNA or complexes thereof repression is concerned, this is conveniently aimed at post-transcription gene silencing. DNA or RNA may be administered or a complex comprising RNAi or a chemical analog thereof specific for HBV mRNA may be employed.

All such molecules may be incorporated into pharmaceutical compositions.

In another embodiment, the present invention provides a biological composition comprising a variant HBV or an HBsAg or L, M or S proteins from said variant HBV or a recombinant or derivative form thereof or its chemical equivalent.

Generally, if an HBV is used, it is first attenuated. The biological composition according to this aspect of the present invention generally fisher comprises one or more pharmaceutically acceptable carriers and/or diluents.

The biological composition may comprise HBsAg or like molecule from one HBV variant or the composition may be a cocktail of HbsAgs or L, M or S proteins or like molecules from a range of ADV- and/or LMV- and/or, FTC- and/or TFV-resistant HBV variants. Similar inclusions apply where the composition comprises an HBV.

The present invention is further directed to the use of defective HBV variants in the manufacture of therapeutic vaccines to vaccinate individuals against infection by HBV strains having a particular nucleotide sequence or encoding a particular polymerase or surface antigen or L, M or S proteins.

Examples of suitable vaccine candidates are defective forms of HBV variants comprising a mutation selected from, in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131N and rtY135C; in another embodiment, rt/N/S/T/I/V53D, rtY126Q, rtI180M, rtS202G, rtI204V and rtI235I/M; in a farther embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA181T, rtK212R, rtL217R, rtS219A, rtN236T and rtN238D; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A; in still another embodiment rtH90D and rtL/F108L; in even yet another embodiment, rtL157L/M, rtA181V and rtV207I; in even still another embodiment, rtL80V, rtP109S, rtI163V, rtL229M and rtN/H/A/S/Q238K; in another embodiment, rtS78S/T, rtN118N/S, rtN139N/K, rtV142E, rtA181A/T, rtI204M, rtQ/P/S/Stop215Q, rtE218K/E and rtN238N/H; in a further embodiment, sP120T, sM125T and sT127A; in yet another embodiment, sT118R, sM133T, SF134V, sI195M, sS207R and sY225Y/C; in still another embodiment, sS126T, sM133L/M, sS143S/T, sD144A, sG145A and sW172Stop; in even yet another embodiment, sN40S, sC69Stop, sM75I, sL88P, sT118A, sW182STOP, sW196L, sY206H and sY225F; in even still another embodiment, s181M and sP214Q; in another embodiment, sF83S, sL173F and sW199L; in a further embodiment, sI126T, sK160R, sS174N, sA184V, sW196L, sS210N, sF/C220L and sY221C; in yet another embodiment, sC69Stop/C, sC76Y sI110V/I, sY134N, sW172Stop/W, sW196Stop and sS207R; in still another embodiment, rtK32, rtN33, rtP34, rtH35 and rtT37; in even yet another embodiment, rtP59, rtK60, rtF61, rtA62 and rtV63; in even still another embodiment, rtD83, rtV84, rtS85, rtA86, rtY89, rtH90 and rtI/L91; in another embodiment, rtP177, rtF178, rtL179, rtL180, rtA181, rtQ182, rtF183 and rtT184; in a further embodiment, rtM204 and rtY203; in yet another embodiment, rt235, rt236, rt237, rt238 and rt239 in still another embodiment, rt247, rt248, rt249, rt250 and rt251; and in even yet another embodiment,

K32M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; N33D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; P34S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; H35I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; T37W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P59S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; K60M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; F61P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; A62R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; V63A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; D83C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/deletion; V84A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; S85T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; A86R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; Y89V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; H90I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; I/L91K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/deletion; P177S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; F178P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/L/K/M/deletion; L179K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/HI/deletion; L180K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; A181R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/Y/V/deletion; Q183E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; F183P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; T184W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; Y203 V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; M204F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; L235K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N236D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; T237W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P237S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; N238D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H238I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; A238R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; S239T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; Q238E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; K239M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; L247K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N248D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H248I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; F249P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/KM/deletion; M250F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; G251H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/deletion; and

V251A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/I/T/W/Y/deletion or a combination of two or more mutations.

In one embodiment, for example, an HBV variant may be identified having a particular mutation in its polymerase conferring resistance or decreased sensitivity to a nucleoside analog. This variant may then be mutated to render it defective, i.e. attenuated or unable to cause infection. Such a defective, nucleoside analog-resistant virus may then be used as a therapeutic vaccine against virulent viruses having the same mutation in its polymerase.

The subject invention extends to kits for assays for variant HBV resistant to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LAS and TFV. Such kits may, for example, contain the reagents from PCR or other nucleic acid hybridization technology or reagents for immunologically based detection techniques. A particularly useful assay includes the reagents and components required for immobilized oligonucleotide- or oligopeptide-mediated detection systems.

Still another aspect of the present invention contemplates a method for determining the potential for an HBV to exhibit reduced sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and Lam or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV and/or optionally other nucleoside or nucleotide analogs or other anti-HBV agents or combination thereof, said method comprising isolating DNA or corresponding mRNA from said HBV and screening for a mutation in the nucleotide sequence encoding HBV DNA polymerase resulting in at least one amino acid substitution, deletion and/or addition in any one or more of domains F and G, and domains A through to E or a region proximal thereto of said DNA polymerase and associated with resistance or decreased sensitivity to ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV, wherein the presence of such a mutation is an indication of the likelihood of resistance to said ADV, LMV, TFV, or FTC, or ADV and LMV, ADV and TFV, LMV and TFV, FTC and ADV, FTC and TFV, FTC and LMV, or ADV and LMV and TFV, or ADV and FTC and TFV, TFV and FTC and LMV, ADV and LMV and FTC, or ADV and FTC and LMV and TFV.

An assessment of a potential viral variant is important for selection of an appropriate therapeutic protocol. Such an assessment is suitably facilitated with the assistance of a computer programmed with software, which inter alia adds index values (I_(V)s) for at least two features associated with the viral variants to provide a potency value (P_(A)) corresponding to the resistance or sensitivity of a viral variant to a particular chemical compound or immunological agent. The I_(V)s can be selected from (a) the ability to exhibit resistance for reduced sensitivity to a particular compound or immunological agent; (b) an altered DNA polymerase from wild-type HBV; (c) an altered surface antigen from wild-type HBV; or (d) morbidity or recovery potential of a patient. Thus, in accordance with the present invention, I_(V)s for such features are stored in a machine-readable storage medium, which is capable of processing the data to provide a P_(A) for a particular viral variant or a biological specimen comprising same.

Thus, in another aspect, the invention contemplates a computer program product for assessing the likely usefulness of a viral variant or biological sample comprising same for determining an appropriate therapeutic protocol in a subject, said product comprising:

-   (1) code that receives as input I_(V)s for at least two features     associated with said viral agents or biological sample comprising     same, wherein said features are selected from.     -   (a) the ability to exhibit resistance for reduced sensitivity to         a particular compound or immunological agent;     -   (b) an altered DNA polymerase from wild-type HBV;     -   (c) an altered surface antigen from wild-type HBV;     -   (d) morbidity or recovery potential of a patient; or     -   (e) altered replication capacity (increased or decreased);     -   (2) code that adds said I_(V)s to provide a sum corresponding to         a P_(V) for said viral variants or biological samples; and -   (3) a computer readable medium that stores the codes.

In a related aspect, the invention extends to a computer for assessing the likely usefulness of a viral variant or biological sample comprising same in a subject, wherein said computer comprises:

-   (1) a machine-readable data storage medium comprising a data storage     material encoded with machine-readable data, wherein said     machine-readable data comprise I_(V)s for at least two features     associated with said viral variant or biological sample; wherein     said features are selected from:—     -   (a) the ability to exhibit resistance for reduced sensitivity to         a particular compound or immunological agent;     -   (b) an altered DNA polymerase from wild-type HBV;     -   (c) an altered surface antigen from wild-type HBV;     -   (d) morbidity or recovery potential of a patient; or     -   (e) altered replication capacity (increased or decreased); -   (2) a working memory for storing instructions for processing said     machine-readable data; -   (3) a central-processing unit coupled to said working memory and to     said machine-readable data storage medium, for processing said     machine readable data to provide a sum of said I_(V)s corresponding     to a P_(V) for said compound(s); and -   (4) an output hardware coupled to said central processing unit, for     receiving said P_(V).

Any general or special purpose computer system is contemplated by the present invention and includes a processor in electrical communication with both a memory and at least one input/output device, such as a terminal. FIG. 19 shows a generally suitable computer system. Such a system may include, but is not limited, to personal computers, workstations or mainframes. The processor may be a general purpose processor or microprocessor or a specialized processor executing programs located in RAM memory. The programs may be placed in RAM from a storage device, such as a disk or pre-programmed ROM memory. The RAM memory in one embodiment is used both for data storage and program execution. The computer system also embraces systems where the processor and memory reside in different physical entities but which are in electrical communication by means of a network.

In an alternative embodiment, the program screens for a mutation selected from, in one embodiment, rtS21A, rtL122F, rtN124H, rtH126R, rtT28N, rtP130Q, rtD131N and rtY135C; in another embodiment, rt/N/S/T/I/V53D, rtY126Q, rtL180M, rtS202G, rtI204V and rtI235I/M; in a further embodiment, rtN53D, rtY54H, rtS57P, rtL91I, rtS116P, rtF122L, rtY124H, rtV134D, rtY141Y/F, rtL145M, rtF151F/Y, rtA181T, rtK212R, rtL217R, rtS219A, rtN236T and rtN238D; in yet another embodiment, rtS78T, rtV84M, rtY126C, rtV1911, rtM204I and rtV214A; in still another embodiment rtH90D and rtL/F108L; in even yet another embodiment, rtL157L/M, rtA181V and rtV207I; in even still another embodiment, rtL80V, rtP109S, rtI163V, rtL229M and rtN/H/A/S/Q238K; in another embodiment, rtS78S/T, rtN118N/S, rtN139N/K, rtV142E, rtA181A/T, rtI204M, rtQ/P/S/Stop215Q, rtE218K/E and rtN238N/H; in a further embodiment, sP120T, sM125T and sT127A; in yet another embodiment, sT118R, sM133T, SF134V, s1195M, sS207R and sY225Y/C; in still another embodiment, sS126T, sM133L/M, sS143S/T, sD144A, sG145A and sW172Stop; in even yet another embodiment, sN40S, sC69Stop, sM751, sL88P, sT118A, sW182STOP, sW196L, sY206H and sY225F; in even still another embodiment, s181M and sP214Q; in another embodiment, sF83S, sL173F and sW199L; in a further embodiment, s1126T, sK160R, sS174N, sA184V, sW196L, sS210N, sF/C220L and sY221C; in yet another embodiment, sC69Stop/C, sC76Y sI110V/I, sY134N, sW172Stop/W, sW196Stop and sS207R; in still another embodiment, rtK32, rtN33, rtP34, rt1135 and rtT37; in even yet another embodiment, rtP59, rtK60, rtF61, rtA62 and rtV63; in even still another embodiment, rtD83, rtV84, rtS8S5, rtA86, rtY89, rtH90 and rtI/L91; in another embodiment, rtP177, rtF178, rtL179, rtL180, rtA181, rtQ182, rtF183 and rtT184; in a further embodiment, rtM204 and rtY203; in yet another embodiment, rt235, rt236, rt237, rt23S and rt239 in still another embodiment, rt247, rt248, rt249, rt250 and rt251; and in even yet another embodiment,

K32M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; N33D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; P34S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; H35I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; T37W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P59S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; K60M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; F61P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; A62R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; V63A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; D83C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/deletion; V84A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/deletion; S85T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; A86R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/YV/deletion; Y89V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; H90I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; I/L91K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/deletion; P177S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; F178P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/L/K/M/deletion; L179K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/HI/deletion; L180K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; A181R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/Y/V/deletion; Q183E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; F183P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/deletion; T184W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; Y203V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/deletion; M204F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; L235K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N233D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; T237W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/deletion; P237S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/deletion; N238D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H238I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; A238R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/deletion; S239T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/deletion; Q238E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/deletion; K239M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/deletion; L247K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/deletion; N248D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/deletion; H248I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/deletion; F249P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/KM/deletion; M250F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/deletion; G251H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/deletion; and

V251A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/I/T/W/Y/deletion or a combination of two or more mutations.

The present invention is further described by the following non-limiting Examples.

EXAMPLE 1 Overlapping Genome of HBV

The overlapping genome of HBV is represented in FIG. 1. The gene encoding DNA polymerase (P), overlaps the viral envelope genes, Pre-S I and Pre-S2, and partially overlaps the X and core (C) genes. The HBV envelope comprises small, middle and large proteins HBV surface antigens. The large protein component is referred to as the HBV surface antigen (HBsAg) and is encoded by the S gene sequence. The Pre-S1 and Pre-S2 gene sequences encode the other envelope components.

EXAMPLE 2 Patients and Treatment

Patient A, a 48 year old Lebanese woman was initially referred for evaluation of thrombocytopenia and hepatosplenomegaly. At this time the patient had abnormal LFT's (ALT 67 U/L, normal<55) and the HBV DNA was 61 pg/ml (231 days prior to the start of treatment). The patient was HBsAg and HBeAg positive. The ALT's fluctuated between 50-70 IU/L from (−231 to −35 days pretreatment). ADV was commenced on Day 0 in a clinical trial on 30 mg/day. HBV DNA levels were reduced with ADV treatment. The ADV treatment was reduced to 10 mg/day (144 days post-treatment). There was a problem with the randomization treatment protocol. The patient was on antiviral treatment for 1 month only during the second year of the treatment period. The study was completed on Day 679 post ADV treatment. The patient was not on ADV treatment until the open label ADV was recommenced on Day 875 from the start of the initial ADV treatment. This second period of ADV treatment was given for 108 days (day 983 post initial ADV treatment). The HBV DNA levels remained at 7-10 pg/ml (1.96×10⁵ to 2.8×10⁵ copies/ml). At Day 983, ADV treatment was stopped and the patient was treated with LMV.

Patient B is a male liver transplant patient. The patient has been on both sequential and combination antiviral therapy including HBIG, FCV+HBIG, LMV+HBIG, LMV, LMV+GCV, LMV+FCV+GCV, LMV+GCV and finally LMV+ADV. The patient has been on long term ADV+LMV treatment for over 795 days.

Patient C, is a 58 year old Male. Prior to ADV treatment the patient had abnormal LFT's (ALT 240 IU/L, normal <55) and the HBV DNA was 2×10⁷ copies/ml. ADV was commenced on Day 0 in a clinical trial on 10 mg/day for two years. The average ALT during the two year clinical trial period was 114 IU/L. However, the ALT was rising and at 630 days after the start of ADV treatment the ALT remained high 407 IU/L. Open label ADV was commenced on Day 668 from the start of the initial ADV treatment. This second period of ADV treatment was given for 71 days. The HBV DNA levels remained high during open label ADV treatment (3.7×10⁶ to 1.5×10⁷ copies/ml). The peak ALT during open label ADV treatment was 517 IU/L (Day 738). The next day (Day 739), ADV treatment was stopped and the patient was treated with LMV.

EXAMPLE 3 Detection of Viral Markers

Hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), anti-HiBe and hepatitis B core antigen (HBcAg) specific IgG and IgM were measured using commercially available immunoassays (Abbott Laboratories, North Chicago, Ill., USA). Hepatitis B viral DNA levels were measured using a capture hybridization assay according to the manufacturer's directions (Digene Hybrid Capture II, Digene Diagnostics Inc., Beltsville, Md.). The manufacturers stated cut-off for detecting HBV viremia in clinical specimens was 0.7×10⁶ copies/ml or 2.5 pg/ml, [Hendricks et al., Am J Clin Pathol 104: 537-46, 1995]. HBV DNA levels can also be quantitated using other commercial kits such as Cobas amplification HBV monitor kit (Roche).

EXAMPLE 4 Sequencing of HBV DNA

HBV DNA was extracted from 100 μl of serum as described previously by Aye et al., J. Hepatol. 26: 1148-1153, 1997. Oligonucleotides were synthesized by Geneworks, Adelaide, Australia. Amplification of the HBV polymerase gene has been described by Aye et al., 1997, supra.

The specific amplified products were purified using PCR purification columns from MO BIO Laboratories Inc (La Jolla, Calif.) and directly sequenced using Big Dye terminator Cycle sequencing Ready Reaction Kit (Perkin Elmer, Cetus Norwalk, Conn.). The PCR primers were used as sequencing primers, OS1 5′-GCC TCA TTT TGT GGG TCA CCA TA-3′ (nt 1408-1430) [SEQ ID NO:3], TTA3 5′-AAA TTC GCA GTC CCC AAA-3′(nt2128-2145) [SEQ ID NO:4], JM 5′-TTG GGG TGG AGC CCT CAG GCT-3′(nt1676-1696) [SEQ ID NO:5], TTA4 5′-GAA AAT TGG TAA CAG CGG-3′ (nt 2615-2632) [SEQ ID NO:6], OS2 5′ TCT CTG ACA TAC TTT CCA AT 3′ (nt 2798-2817) [SEQ ID NO:7], to sequence the internal regions of the PCR products.

EXAMPLE 5 Analysis of HBV DNA

Patient A: During ADV treatment, unique HBV mutations were detected by sequencing (Tables 4 and 5) This includes the unique mutation at rtY135C in addition to the mutation at rtT128N that was present prior to ADV treatment. A number of other unique changes were also detected in the polymerase and in the overlapping envelope gene (Table 5, FIGS. 4, 5 and 6). The unique change in the HBsAg include sP120T. These unique changes were compared to reference sequences from each of the seven genotypes A-G as well as a consensus sequence from pretreatment samples to determine unique changes.

Patient B: The HBV mutations prior to ADV treatment and during ADV treatment are listed in Table 6 and 7 and FIGS. 7, 8, and 9. The unique changes in the rt region of the HBV DNA polymerase include rtN/S/T/I/V53D, rtY126Q, rtL180M, rtS202G, rtI204V and rtI235I/M. The unique changes in the HBsAg include sT118R, sM133T, sF134V, sI195M, sS207R, sY225Y/C.

Patient C: The HBV mutations prior to ADV treatment and during ADV treatment are listed in Tables 8 and 9 and FIGS. 10, 11 and 12. The unique changes in the rt region of the HBV DNA polymerase include rtN53D, rtS116P, rtF151F/T, rtN236T and rtN238D. The unique changes in the HBsAg include sG145A and sW172stop.

Patient D: The HBV mutations during ADV treatment is listed in Table 10 and FIGS. 13, 14 and 15. The unique changes in the HBV DNA polymerase include rtS78T, rtV84M, rtY126C, rtV191I, rtM204I and rtV214A. The unique changes in the surface include sN40S and sC69 Stop. A number of unique changes were detected after the stop codon mutation at codon 69 of the S gene including sM75I, sL88P, sT118A, sW182stop, sW196L, sY206H and sY225F.

Patient E: The HBV mutations during ADV treatment is listed in Table 11 and FIGS. 16, 17 and 18. The unique changes in the HBV DNA polymerase include rtH90D and rtL/F108L. The unique changes in the surface include sI81M and sP214Q. A six nucleotide insertion was also detected resulting in a two amino acid insertion in the HBV polymerase and envelope gene at codons rt131 and s122, respectively. This insertion was previously detected in pre-ADV samples.

EXAMPLE 6 Adefovir Dipivoxil (ADV)

ADV (formerly Bis-pom PMEA)) is a potent inhibitor of HBV replication. The structure of ADV is shown in FIG. 2 and its synthesis is described by Benzaria et al., J Med Chem. 39: 4958-4965, 1996).

EXAMPLE 7 HBV rt Mutants

The HBV polymerase has similarities to other polymerases including HIV. Thus, mutations associated with resistance to antiviral agents may occur within the polymerase in functionally important regions such as the nucleotide triphosphate binding pocket that may also include the interaction between the DNA primer and template strand, magnesium ions and nucleoside triphosphates or nucleoside/nucleotide analogs (and there various phosphroylated forms). Codons which are proposed to be mutated during anti-viral selection pressure are rtK32, rt N33, rtP34, rtH35 and rtT37 (that are upstream from the F domain); rt P59, rtK60, rtF61, rtA62 and rtV63 (between the F and A domains), rtD83, rtV84, rtS85, rtA86, rt Y89, rt H90 and rtI/L91 (within the A domain and the region immediately prior to and after), rtP177, rtF178, rt L179, rtL180, rtA181, rtQ182, rtF183 and rtT184 (B domain); rtM204 and rtY203 (C Domain), rtL235, rtN236, rtP/T237, rtN/H/A/S/Q238 and rtK239 (D Domain), rLt247, rtN/H248, rtF249, rtM250 and rtG251 (E Domain). The codons are defined in Table 12 and examples of various mutants are given in Tables 13 and 14.

EXAMPLE 8 Patient F

The HBV mutations during ADV treatment of Patient F are listed in Table 15 and FIGS. 20, 21 and 22. The unique changes in the HBV DNA polymerase includes rtL157L/M, rtA181V, rtV207I, and rtN236T. The unique changes in the surface includes sF83S, sL173F and sW199L.

EXAMPLE 9 Patient G

The HBV mutations during ADV treatment of Patient G are listed in Table 16 and FIGS. 23, 24 and 25. The unique changes in the HBV DNA polymerase includes rtL80V, rtP109S, rtI163V, rtM204I, rtL229M and rtN/H/A/S/Q238K. The unique changes in the surface includes sI126T, sK160R, sS174N, sA184V, sW196L, sS210N, sF/C220L and sY221C.

EXAMPLE 10 Patient H

The HBV mutations during ADV treatment in Patient H are listed in Table 17 and FIGS. 26, 27 and 28. The unique changes in the HBV DNA polymerase includes rtS78S/T, rtN118N/S, rtN139N/K, rtV142E, rtA181A/T, rtI204M, rtQ/P/S/Stop215Q, rtE218K/E, and rtN238N/H. The unique changes in the surface include sC69Stop/C, sC76Y sI110V/I, sY134N, sWI72Stop/W, sW196Stop and sS207R.

EXAMPLE 11 In Vitro Analysis of ADV Resistance

The sensitivity/resistance profile of HBV mutants to ADV was examined in vitro using recombinant HBV/baculovirus. The procedure for analyzing the resistance profile is outlined in the following Examples 12-20.

EXAMPLE 12 Cell Culture

Sf21 insect cells were maintained in supplemented Grace's insect medium further supplemented with 10% v/v heat-inactivated fetal bovine serum (Gibco BRL, Gaithersburg, Md.) in humidified incubator at 28° C. with CO₂ HepG2 cells were maintained in minimal essential medium supplemented with 10% v/v heat-inactivated fetal bovine serum (MEM-FBS). HepG2 cells were grown in humidified 37° C. incubators at 5% v/v Col.

EXAMPLE 13 Preparation of HBV/Baculovirus Transfer Vector with Specific Point Mutations

The recombinant HBV/baculovirus system used for antiviral testing has been previously described (Delaney et al., Antimicrob Agents Chemother 45(6). 1705-1013, 2001). In brief, the recombinant transfer vector was created by excising a fragment containing the 1.3×HBV genome construct and cloning it into the multiple cloning region of a baculovirus vector pBlueBac4.5 (Invitrogen, Carlsbad, Calif.). Point mutations were created by site directed mutagenesis using the commercial kits according to the manufacturer's specifications (QuikChange, Stratagene). HBV/baculovirus recombinant clones encoding the reverse transcriptase mutations rtA181T/N236T/N238D and rtN236T/N236D in combination with the precore mutation at G1896A (pcW2S stop) or wild-type with respect to codon pcW28, were prepared by site-directed mutagenesis. The nucleotide sequence of the plasmid and the point mutations generated by site directed mutagenesis were confirmed by sequencing using the ABI Prism Big Dye Terminator Cycle Sequencing Ready Reaction Kit according to the manufacturer's specifications (Perkin Elmer, Cetus Norwalk, Conn.).

EXAMPLE 14 Generation of Recombinant Baculoviruses Containing the 1.3 HBV Construct

Purified recombinant transfer vector and linear AcMNPV baculovirus DNA were co-transfected into Sf21 cells using the BacNBlue transfection kit from Invitrogen (Carlsbad, Calif.); recombinant viruses were isolated by plaque assay according to the manufacturer's instructions. A series of recombinant viruses were amplified from isolated plaques by infecting 100-mm dishes of Sf21 cells. Viral DNA was extracted from amplified viruses using standard procedures. Purified viral DNA was digested with restriction enzymes and then fractionated by electrophoresis in a 1% v/v agarose gel. Southern blotting was performed to determine which virus isolates contained the intact 1.3 HBV construct. A Boehringer Mannheim Random Prime DNA Labeling kit (Indianapolis, Ind.) was used to generate [P³²]-radiolabeled probes. A full-length double-stranded HBV genome was used as a template for all radiolabeled probes. Viral DNA sequence was confirmed by PCR amplification of the polymerase catalytic region using the sense primer 5′-GCC TCA TTT TGT GGG TCA CCA TA-3′ [SEQ ID NO:8], (nucleotide 1408 to 1430 according to HBV Genebank Accession number M38454) and the antisense primer 5′-TCT CTG ACA TAC TTT CCA AT-3′ [SEQ ID NO:9] (nucleotides 2817 to 2798 according to HBV Genebank Accession number M38454). The following primers were utilized for the sequencing of internal regions 5′-TGC ACG ATT CCT GCT CAA-3′ [SEQ ED NO:10] (nucleotides 2345-2362 according to HBV Genebank Accession number M38454) and 5′-TTT CTC AAA GGT GGA GAC AG-3′ [SEQ ID NO: 11] (nucleotides 1790-1810 according to HBV Genebank Accession number M38454).

EXAMPLE 15 Preparative Baculovirus Amplification and Purification

Baculoviruses were amplified by infecting suspension cultures of Sf21 cells in log phase at a multiplicity of infection (moi) of 0.5 pfu/cell. Infections were allowed to proceed until a majority of the cells in the flasks showed visible signs of infection (four to five days). Virions were concentrated from infected Sf21 medium by centrifugation at 80,000×g and purified through a 20-60% w/v sucrose gradient. Purified virus was titrated in quadruplicate in Sf21 cells by end-point dilution. An aliquot of each high titer stock was used for DNA extraction. The polymerase gene was amplified and sequenced to confirm the presence of the site-directed mutagenesis as in Example 14.

EXAMPLE 16 Infection of HepG2 Cells with Recombinant HBV Expressing Baculovirus

HepG2 cells were seeded at approximately 20-40% confluency and then were grown for 16-24 hours before infection. On the day of infection, triplicate plates of cells were trypsinized, and viable cell number was determined with a hemocytometer using Trypan blue exclusion. Average cell counts were calculated and used to determine the volume of high-titer viral stock necessary to infect cells at the indicated moi. HepG2 cells were washed one time with serum-free MEM to remove traces of serum. Baculovirus was diluted into MEM without serum to achieve the appropriate moi using volumes of 1.0, 0.5, and 0.25 ml to infect 100-nm, 601-nm, and 35-mm dishes, respectively. Baculovirus was adsorbed to HepG2 cells for one hour at 37° C. with gentle rocking every 15 minutes to ensure that the inoculum was evenly distributed. The inoculum was then aspirated and HepG2 cells were washed two times with phosphate-buffered saline and refed MEM-FBS with or without various concentrations of agents.

EXAMPLE 17 Detection of Intracellular Replicative Intermediates

HBV core particles were isolated from the cytoplasmic fraction of HepG2 cells lysed in 0.5 w/v NP-40. Cytoplasmic extracts were adjusted to 10 mmol/l McC12 and unprotected DNA was removed by an incubation to 500 g/ml Proteinase K for 1.5 hours at 37° C. HBV DNA in the samples were then extracted using commercial DNA extraction kits such as Qiagen (DNA extraction) or in-house methods using sequential phenol and chloroform extractions, and the nucleic acids were recovered by ethanol precipitation. Nucleic acids were resuspended in 50 μl/l TE (10 mmol/l Tris, 1 mmol/l ethylenediaminetetraacetic acid), normalized by OD260, and digested with 100 g/ml, RNase (Boehringer Mannheim, Indianapolis, Ind.) for one hour at 37° C. before analysis by real-time PCR or electrophoresis and Southern blotting. After southern blot analysis a BioRad GS-670 imaging densitometer and the Molecular Analyst software (BioRad, Hecules Califoria) was used to analyze suitable exposures of Southern blots. Densitometry data was fitted to logistic dose response curves using the TableCurve 2D software package from Jandel Scientific. Logistic dose response equations were used to calculate IC₅₀ and IC₉₀ values and coefficients of variation.

EXAMPLE 18 Real-Time PCR

For the real-time PCR based assay for HBV, HBV DNA was extracted from 200 μl of serum using the QIAamp DNA Mini Kit according to the manufacturer's instructions (QIAGEN GmbH, Hildens, Germany). Primers and a molecular beacon were designed for conserved nucleic acid sequences within the precore domain of the HBV genome to amplify and detect a 216-nucleotide product. Amplification was performed in a 50-μl reaction mixture containing 1.0 Taqman buffer A (Applied Biosystems, Foster City, Calif.), 3.0 in M MgCl, 0.4 pmol of each primer per μL, forward primer, PC1 (5′-GGGAGGAGATTAGGTTAA-3′ [SEQ ID NO:12]) and reverse primer, PC2 (5′-GGCAAAAACGAGAGTAACTC-3′ [SEQ ID NO:13]), 0.4 pmol of the HBV-specific molecular beacon per μL, (5′-FAM-CGCGTCCTACTGTTCAAGCCTCCAAGCTGT GACGCG-DABCYL-3′ [SEQ ID NO:14]; where FAM represents fluorophore 6-carboxyfluorescein and DABCYL, 4-dimethylaminophenylazobenzoic acid, a quenching chromophore) and 1.25 U of AmpliTaq Gold DNA polymerase (Perkin-Elmer). PCR was performed using the ABI PRISM 7700 spectrofluorometric thermocycler (Applied Biosystems). The PCR program consisted of an initial cycle (95° C. for 10 minutes) followed by 45 amplification cycles (94° C. for 15 sees, 50° C. for 30 sees, 72° C. for 30 sees). The instrument detected and recorded the fluorescence spectrum of each reaction tube during the annealing phase.

An external standard was constructed by ligation of a 1.3 kB wild-type HBV plasmid (genotype D) into the pBlueBac plasmid vector (Hershey Medical Center, Hershey, Pa.). Quantification of the DNA concentration of the plasmid was determined by spectrophotometry. Duplicates of serial 10-fold dilutions of the plasmid ranging from 108 copies/ml to 100 copies/ml were included in each run in order to generate a standard curve.

The copy number in each experimental reaction was determined by interpolation of the derived threshold cycle (CT).

EXAMPLE 19 ADV Treatments

ADV was resuspended in sterile water, aliquoted, and frozen at −20° C. to avoid repeated freezing and thawing of the drug. Medium containing ADV was prepared daily as needed using fresh aliquots of 3TC. In experiments in which ADV treatment was initiated after viral infection, HepG2 cells were exposed to the indicated concentration of ADV immediately after infection with HBV baculovirus. In experiments utilizing pretreatment with ADV, cells were fed medium containing ADV 16 hours prior to HBV baculovirus infection, HBV baculovirus infection was also carried out in medium containing ADV, and cells were refed fresh medium containing ADV immediately after completion of the infection and washing procedures.

EXAMPLE 20 Antiviral Testing Performed with Wild-Type and HBV/Baculovirus Encoding rtA181T/N236T/N238D and rtN236T/N236D

The in vitro antiviral drug cross-resistance testing of the HBV mutants is shown in Table 18. The laboratory reference strain of HBV (genotype D subtype ayw) containing the introduced D domain mutations demonstrated increased IC₅₀ values against ADV (Table 18). The rt N236T/N238D mutation was associated with a twenty-three fold increase in IC₅₀ against ADV. This was reduced to a five-fold increase when the rtA181T was also present and this triple HBV polymerase mutant was resistant to LMV.

TABLE 4 Clinical, virological and HBV sequencing data summary for Patient A while on open label ADV. Days HBV DNA Key polymerase post-ADV copies/ml ALT Treatment mutations detected treatment (pg/ml) IU/L protocol by sequencing¹ −230 1.7 10⁶ (61) 67 U/L pre-therapy rtT/N128T/N rtQ/H/R215Q/stop 875 ADV recommenced 904 1.55 × 10⁶ 932 2.97 × 10⁶ 959 1.76 × 10⁶ 983 1.64 × 10⁶ 65 end ADV rtT128N rtY135C ¹Nomenclature according to Stuyver et al., 2001, supra

TABLE 5 Summary of HBV mutations in patient A treated with ADV Days Sample post-ADV name treatment Genotype Polymerase* Surface ILA1 −230 D rtA/S21A/S sP120P/T rtT/N128T/N** sI208I/L rtQ/H/R215Q/stop ILA2 904 D rtA/S21S sP/T120P rtF122L sT125M rtR126H sI/I208I/L rtT/N128T/N rtQ130P rtN131D rtQstop/215Q rtH248N ILA3 932 D rtA/S21S sP/T120P rtF122L sT125M rtR126H sI/I208I/L rtT/N128T/N rtQ130P rtN131D rtQstop/215Q rtH248N ILA4 983 D rtS21A sP120T rtL122F sM125T rtN124H sT127A rtH126R rtT128N rtP130Q rtD131N rtY135C *Nomenclature according to Stuyver et al., 2001, supra. **Mutations in bold have not been detected in reference HBV genotypes, mutations not in bold are changes from the previous sample that are present in reference genotypes.

TABLE 6 Clinical, virological and HBV sequencing data summary for Patient B while on open label ADV. Key polymerase Days HBV DN mutations post-ADV copies/ml ALT Treatment detected treatment (pg/ml) IU/L protocol by sequencing¹ −867(S0)  183 298 pre-therapy rtN/S/T/I/V53D rtV153G rtQ/E215S rtN248H −8(S6) 955 427 pre-ADV on rtI/L80L LMV rtY126Q rtL180M rtS202G rtI204V 76(S8) not detected 150 on ADV (20 mg) rtN/S/T/I/V53D and LMV rtY126Q rtL180M rtS202G rtI204V 637(S12) not detected 36 on ADV (5 mg) rtN/S/T/I/V53D and LMV rtY126Q rtL180M rtS202G rtI204V 872(S15) not detected 67 on ADV (5 mg) rtN/S/T/I/V53D and LMV rtY126Q rtL180M rtS202G rtI204V rtI235I/M ¹Nomenclature according to Stuyver et al., 2001, supra

TABLE 7 Summary of HBV mutations in Patient B treated with ADV Sample Days post-ADV name treatment Genotype Polymerase* Surface S0 −867 D rtN/S/T/I/V53D sM/K/L133T rtV153G sF134V rtQ/E215S sS207R rtN248H sL21V/L S6 −8 D rtI/L80L sT118R rtY126Q sM133T rtL180M sF134V rtS202G sI195M rtI204V sS207R S8 76 D rtN/S/T/I/V53D sT118R rtY126Q sM133T rtL180M sF134V rtS202G sI195M rtI204V sS207R S12 637 D rtN/S/T/I/V53D sT118R rtY126Q sM133T rtL180M sF134V rtS202G sI195M I204V sS207R S15 872 D rtN/S/T/I/V53D sT118R rtY126Q sM133T rtL180M sF134V rtS202G sI195M rtI204V sS207R rtI235I/M sY225Y/C *Nomenclature according to Stuyver et al., 2001, supra **Mutations in bold have not been detected in reference HBV genotypes, mutations not in bold are changes from the previous sample that are present in reference genotypes.

TABLE 8 Clinical, virological and HBV sequencing data summary for Patient C while on open label ADV. HBV Key polymerase Days DNA mutations post-ADV copies/ml ALT detected by treatment (pg/ml) IU/L Treatment protocol sequencing¹ −26   2 × 10⁷ pre-therapy rtN53D rtS116P rtD/N/S134V rtN238D 0 240 ADV commenced clinical trial 29 160 630 407 668 Open label ADV 701 1.5 × 10⁷ 226 730 3.7 × 10⁶ 361 rtN53D rtS116P rtF151S/T rtA181T rtN236T rtN238D 738 517 739 end ADV, start LMV ¹Nomenclature according to Stuyver et al., 2001, supra

TABLE 9 Summary of HBV mutations in Patient C treated with ADV Sample Days post-ADV name treatment Genotype Polymerase* Surface DRJ1299 −26 D rtN53D** T126S rtY54H S204G rtS57P L209V rtL91I S210R rtS116P rtF122L rtY124H rtD/N/S134V rtK212R rtL217R rtS219A rtN238D DRJ1 730 D rtN53D sS126T rtY54H sM133L/M rtS57P sS143S/T rtL91I sD144A rtS116P sG145A rtF122L sW172Stop rtY124H rtV134D rtY141Y/F rtL145M rtF151T/F rtA181T rtK212R rtL217R rtS219A rtN236T rtN238D *Nomenclature according to Stuyver et al., 2001, supra. **Mutations in bold have not been detected in reference HBV genotypes, mutations not in bold are changes from the previous sample that are present in reference genotypes.

TABLE 10 Summary of HBV mutations in Patient D treated with ADV Sample Name Genotype Polymerase* Surface 02575908 D rtS78T sN40S rtV84M sC69stop rtY126C sM75I rtV191I sL88P rtM204I sT118A rtV214A sW182STOP sW196L sY206H sY225F *Nomenclature according to Stuyver et al., 2001, supra. **Mutations in bold have not been detected in reference HBV genotypes, mutations not in bold are changes from the previous sample that are present in reference genotypes.

TABLE 11 Summary of HBV mutations in Patient E treated with ADV Sample Name Genotype Polymerase* Surface 8123/02 A rtH90D sI81M rtL/F108L sY/S100Y 6nt 6nt insertion/ insertion/duplication duplication after after codon codon s122 (aaT & K) rt131(aaQ&N) sP214Q *Nomenclature according to Stuyver et al., 2001, supra. **Mutations in bold have not been detected in reference HBV genotypes, mutations not in bold are changes from the previous sample that are present in reference genotypes.

TABLE 12 Codons where mutations occur following exposure to nucleoside or nucleotide analogs Original amino acid in reverse transcriptase Region/ (rt) and codon Domain position Nucleotide prior to F K32 AAG AAA N33 AAT P34 CCT H35 CAC T37 ACC F TO A P59 CCA K60 AAA P61 TTC A62 GCA V63 GTC A D83 GAT V84 GTG S85 TCT A86 GCG Y89 TAT H90 CAT I/L91 ATT CTT B P177 CCG F178 TTT L179 CTC L180 CTG A181 TTG Q182 CAG P183 TTT T184 ACT C Y203 TAT M204 ATG D L235 TTG TTA N236 AAC AAT T237 ACT ACC P237 CCT CCC N238 AAT AAC H238 CAC A238 GCT S238 TCT Q238 CAG K239 AAA AAG E L247 CTT TTA CTA CTC CTG N248 AAC AAT H248 CAT CAC F249 TTC TTT M250 ATG G251 GGT GGA GGC GGG V251 GTC

TABLE 13 Target amino acid sites in rt with codons and mutations leading to amino acid changes.

Amino Amino Amino Title Codon Acid Codon Acid Codon Acid K32 AAG Lys AAG Lys GAG Glu N33 AAT Asn AAT Asn GAT Asp P34 CCT Pro ACT Thr GCT Ala H35 CAC His AAC Asn GAC Asp T37 ACC Thr ACC Thr GCC Ala P59 CCA Pro ACA Thr GCA Ala K60 AAA Lys AAA Lys GAA Glu F61 TTC Phe ATC Ile GTC Val A62 GCA Ala ACA Thr GCA Ala V63 GTC Val ATC Ile GTC Val D83 GAT Asp AAT Asn GAT Asp V84 GTG Val ATG Met GTG Val S85 TCT Ser ACT Thr GCT Ala A86 GCG Ala ACG Thr GCG Ala Y89 TAT Tyr AAT Asn GAT Asp H90 CAT His AAT Asn GAT Asp I/L91 ATT Ile ATT Ile GTT Val P177 CCG Pro ACG Thr GCG Ala F178 TTT Phe ATT Ile GTT Val L179 CTC Leu ATC Ile GTC Val L180 CTG Leu ATG Met GTG Val A181 TTG Leu ATG Met GTG Val Q183 CAG Gln AAG Lys GAG Glu F183 TTT Phe ATT Ile GTT Val T184 ACT Thr ACT Thr GCT Ala Y203 TAT Tyr AAT Asn GAT Asp M204 ATG Met ATG Met GTG Val L235 TTG Leu ATG Met GTG Val N236 AAC Asn AAC Asn GAC Asp T237 ACT Thr ACT Thr GCT Ala P237 CCT Pro ACT Thr GCT Ala N238 AAT Asn AAT Asn GAT Asp H238 CAC His AAC Asn GAC Asp A238 GCT Ala ACT Thr GCT Ala S239 TCT Ser ACT Thr GCT Ala Q238 CAG Gln AAG Lys GAG Glu K239 AAA Lys AAA Lys GAA Glu L247 CTT Leu ATT Ile GTT Val N248 AAC Asn AAC Asn GAC Asp H248 CAT His AAT Asn GAT Asp F249 TTC Phe ATC Ile GTC Val M250 ATG Met ATG Met GTG Val G251 GGT Gly AGT Ser GGT Gly V251 GTC Val ATC Ile GTC Val (II) Codon Amino Acid Codon Amino Acid Codon Amino Acid CAG Gln TAG Stop AAG Lys CAT His TAT Tyr AAT Asn CCT Pro TCT Ser CAT His CAC His TAC Tyr CAC His CCC Pro TCC Ser AAC Asn CCA Pro TCA Ser CAA Gln CAA Gln TAA Stop AAA Lys CTC Leu TTC Phe TAC Tyr CCA Pro TCA Ser GAA Glu CTC Leu TTC Phe GAC Asp CAT His TAT Tyr GAT Asp CTG Leu TTG Leu GAG Glu CCT Pro TCT Ser TAT Tyr CCG Pro TCG Ser GAG Glu CAT His TAT Tyr TAT Tyr CAT His TAT Tyr CAT His CTT Leu TTT Phe AAT Asn CCG Pro TCG Ser CAG Gln CTT Leu TTT Phe TAT Tyr CTC Leu TTC Phe CAC His CTG Leu TTG Leu CAG Gln CTG Leu TTG Leu TAG Stop CAG Gln TAG Stop CAG Gln CTT Leu TTT Phe TAT Tyr CCT Pro TCT Ser AAT Asn CAT His TAT Tyr TAT Tyr CTG Leu TTG Leu AAG Lys CTG Leu TTG Leu TAG Stop CAC His TAC Tyr AAC Asn CCT Pro TCT Ser AAT Asn CCT Pro TCT Ser CAT His CAT His TAT Tyr AAT Asn CAC His TAC Tyr CAC His CCT Pro TCT Ser GAT Asp CCT Pro TCT Ser TAT Tyr CAG Gln TAG Stop CAG Gln CAA Gln TAA Stop AAA Lys CCT Leu TTT Phe CAT His CAC His TAC Tyr AAC Asn CAT His TAT Tyr CAT His CTC Leu TTC Phe TAC Tyr CTG Leu TTG Leu AAG Lys CGT Arg TGT Cys GAT Asp CTC Leu TTC Phe GAC Asp (III) Codon Amino Acid Codon Amino Acid Codon Amino Acid AGG Arg ACG Thr ATG Met AGT Ser ACT Thr ATT Ile CGT Arg CCT Pro CTT Leu CGC Arg CCC Pro CTC Leu AGC Ser ACC Thr ATC Ile CGA Arg CCA Pro CTA Leu AGA Arg ACA Thr ATA Ile TGC Cys TCC Ser TTC Phe GGA Gly GCA Ala GTA Val GGC Gly GCC Ala GTC Val GGT Gly GCT Ala GTT Val GGG Gly GCG Ala GTG Val TGT Cys TCT Ser TTT Phe GGG Gly GCG Ala GTG Val TGT Cys TCT Ser TTT Phe CGT Arg CCT Pro CTT Leu AGT Ser ACT Thr ATT Ile CGG Arg CCG Pro CTG Leu TGT Cys TCT Ser TTT Phe CGC Arg CCC Pro CTC Leu CGG Arg CCG Pro CTG Leu TGG Trp TCG Ser TTG Leu CGG Arg CCG Pro CTG Leu TGT Cys TCT Ser TTT Phe AGT Ser ACT Thr ATT Ile TGT Cys TCT Ser TTT Phe AGG Arg ACG Thr ATG Met TGG Trp TCG Ser TTG Leu AGC Ser ACC Thr ATC Ile AGT Ser ACT Thr ATT Ile CGT Arg CCT Pro CTT Leu AGT Ser ACT Thr ATT Ile CGC Arg CCC Pro CTC Leu GGT Gly GCT Ala GTT Val TGT Cys TCT Ser TTT Phe CGG Arg CCG Pro CTG Leu AGA Arg ACA Thr ATA Ile CGT Arg CCT Pro CTT Leu AGC Ser ACC Thr ATC Ile CGT Arg CCT Pro CTT Leu TGC Cys TCC Ser TTC Phe AGG Arg ACG Thr ATG Met GGT Gly GCT Ala GTT Val GGC Gly GCC Ala GTC Val (IV) Co- Amino Co- Amino Co- Amino Co- Amino don Acid don Acid don Acid don Acid AAA Lys AAG Lys AAC Asn AAT Asn AAA Lys AAG Lys AAC Asn AAT Asn CCA Pro CCG Pro CCC Pro CCT Pro CAA Gln CAG Gln CAC His CAT His ACA Thr ACG Thr ACC Thr ACT Thr CCA Pro CCG Pro CCC Pro CCT Pro AAA Lys AAG Lys AAC Asn AAT Asn TTA Leu TTG Leu TTC Phe TTT Phe GCA Ala GCG Ala GCC Ala GCT Ala GTA Val GTG Val GTC Val GTT Val GAA Glu GAG Glu GAC Asp GAT Asp GTA Val GTG Val GTC Val GTT Val TCA Ser TCG Ser TCC Ser TCT Ser GCA Ala GCG Ala GCC Ala GCT Ala TAA Stop TAG Stop TAC Tyr TAT Tyr CAA Gln CAG Gln CAC His CAT His ATA Ile ATG Met ATC Ile ATT Ile CCA Pro CCG Pro CCC Pro CCT Pro TTA Leu TTG Leu TTC Phe TTT Phe CTA Leu CTG Leu CTC Leu CTT Leu CTA Leu CTG Leu CTC Leu CTT Leu TTA Leu TTG Leu TTC Phe TTT Phe CAA Gln CAG Gln CAC His CAT His TTA Leu TTG Leu TTC Phe TTT Phe ACA Thr ACG Thr ACC Thr ACT Thr TAA Stop TAG Stop TAC Tyr TAT Tyr ATA Ile ATG Met ATC Ile ATT Ile TTA Leu TTG Leu TTC Phe TTT Phe AAA Lys AAG Lys AAC Asn AAT Asn ACA Thr ACG Thr ACC Thr ACT Thr CCA Pro CCG Pro CCC Pro CCT Pro AAA Lys AAG Lys AAC Asn AAT Asn CAA Gln CAG Gln CAC His CAT His GCA Ala GCG Ala GCC Ala GCT Ala TCA Ser TCG Ser TCC Ser TCT Ser CAA Gln CAG Gln CAC His CAT His AAA Lys AAG Lys AAC Asn AAT Asn CTA Leu CTG Leu CTC Leu CTT Leu AAA Lys AAG Lys AAC Asn AAT Asn CAA Gln CAG Gln CAC His CAT His TTA Leu TTG Leu TTC Phe TTT Phe ATA Ile ATG Met ATC Ile ATT Ile GGA Gly GGG Gly GGC Gly GGT Gly GTA Val GTG Val GTC Val GTT Val

TABLE 14 Amino acid mutations at target sites in rt Target Mutation K32 M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L N33 D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R P34 S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F H35 I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G T37 W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S P59 S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F K60 M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L F61 P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M A62 R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V V63 A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y D83 C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N V84 A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y S85 T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P A86 R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V Y89 V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W H90 I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G I/L91 K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H P177 S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F F178 P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M L179 K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I L180 K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I A181 K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I Q183 E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C F183 P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M T184 W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S Y203 V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W M204 F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K L235 K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I N236 D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R T237 W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S P237 S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F N238 D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R H238 I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G A238 R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V S239 T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P Q238 E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C K239 M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L L247 K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I N248 D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y/V/A/R H248 I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G F249 P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K/M M250 F/P/S/T/W/Y/V/A/R/N/D/C/Q/E/G/H/I/L/K G251 H/I/L/K/M/F/P/S/T/W/Y/V/A/R/N/D/C/Q/E V251 A/R/N/D/C/Q/E/G/H/I/L/K/M/F/P/S/T/W/Y

TABLE 15 Summary of HBV mutations in Patient F treated with ADV Sample Name Genotype Polymerase* Surface CAP 01564808 A rtL157L/M sF83S rtA181V sL173F rtV207I sW199L rtN236T *Nomenclature according to Stuyver et al., 2001, supra. **Mutations in bold have not been detected in reference HBV genotypes, mutations not in bold are changes from the previous sample that are present in reference genotypes.

TABLE 16 Summary of HBV mutations in Patient G treated with ADV Sample Name Genotype Polymerase* Surface KAN 02510355 C rtL80V sI126T rtP109S sK160R rtI163V sS174N rtM204I sA184V rtL229M sW196L rtN/H/A/S/Q238K sS210N sF/C220L sY221C *Nomenclature according to Stuyver et al., 2001, supra. **Mutations in bold have not been detected in reference HBV genotypes, mutations not in bold are changes from the previous sample that are present in reference genotypes.

TABLE 17 Summary of HBV mutations in Patient H treated with ADV Sample Name Genotype Polymerase* Surface LAV0303 D rtS78S/T sC69Stop/C rtN118N/S sC76Y rtN139N/K sI110V/I rtV142E sY134N rtA181A/T sW172Stop/W rtI204M sW196Stop rtQ/P/S/Stop215Q sS207R rtE218K/E rtN238N/H *Nomenclature according to Stuyver et al., 2001, supra. **Mutations in bold have not been detected in reference HBV genotypes, mutations not in bold are changes from the previous sample that are present in reference genotypes.

TABLE 18 In vitro drug susceptibility of the HBV reference laboratory strain and patient-derived HBV isolate In vitro Susceptibility IC₅₀ (fold change from wild-type) Real-time PCR Southern Blot Mutation Adefovir Adefovir Lamivudine Wild-type (pPC) 1 1 1 rt N236T/N238D 23 NA¹ NA¹ rt A181T/N236T/N238D 5.1 7.3 >100 rt L180M/M204V² NT⁵ 0.9 >2500 ¹NA, not analyzed. ²Data from Delaney et al., 2001, supra Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features

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1. An isolated hepatitis B virus (HBV) variant, wherein the variant comprises a nucleotide mutation in a gene encoding an HBV DNA polymerase resulting in an amino acid substitution mutation to the reverse transcriptase (rt) domain of the DNA polymerase of the alanine residue at codon 181, wherein the nucleotide substitution results in a valine in the HBV variant, wherein the HBV variant exhibits decreased sensitivity to adefovir.
 2. A method for determining whether a hepatitis B virus (“test virus”) from a human patient would exhibit reduced sensitivity to adefovir, the method comprising: screening a nucleic acid molecule from the test virus for adefovir-resistant mutations, the nucleic acid molecule comprising a nucleic acid sequence that encodes a reverse transcriptase domain of a DNA polymerase, the mutations comprising a mutation at codon 181, wherein the mutation indicates that the test virus would exhibit reduced sensitivity to adefovir.
 3. The method of claim 2, wherein the mutation at position codon 181 is threonine or valine.
 4. (canceled) 